SKU: 86349818475

Recreations in the Theory of Numbers

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Description

Recreations in the Theory of NumbersNumber theory, the Queen of Mathematics, is an almost purely theoretical science. Yet it can be the source of endlessly intriguing puzzle problems, as this remarkable book demonstrates. This is the first book to deal exclusively with the recreational aspects of the subject and it is certain to be a delightful surprise to all devotees of the mathematical puzzle, from the rawest beginner to the most practiced expert. Almost every aspect of the theory of

Number theory, the Queen of Mathematics, is an almost purely theoretical science. Yet it can be the source of endlessly intriguing puzzle problems, as this remarkable book demonstrates. This is the first book to deal exclusively with the recreational aspects of the subject and it is certain to be a delightful surprise to all devotees of the mathematical puzzle, from the rawest beginner to the most practiced expert. Almost every aspect of the theory of numbers that could conceivably be of interest to the layman is dealt with, all from the recreational point of view. Readers will become acquainted with divisors, perfect numbers, the ingenious invention of congruences by Gauss, scales of notation, endless decimals, Pythagorean triangles (there is a list of the first 100 with consecutive legs; the 100th has a leg of 77 digits), oddities about squares, methods of factoring, mysteries of prime numbers, Gauss's Golden Theorem, polygonal and pyramidal numbers, the Pell Equation, the unsolved Last Theorem of Fermat, and many other aspects of number theory, simply by learning how to work with them in solving hundreds of mathematical puzzle problems. The text is extremely clear and easy to follow, and it bears convincing evidence of the author's deep sense of humor and his outstanding ability to lure the reader through even the most difficult trails by skillfully revealing their fascination. The problems distributed throughout the book are explained in the final chapter and there is also a supplementary chapter containing 100 problems and their solutions, many original. There are over 100 tables.
The appeal of these stimulating puzzles lies in their ready comprehensibility and the fact that only high school math is needed to master the fundamental theory presented by the author. This theory is itself interesting and of use to the more serious math student, but it may be omitted by lay readers without diminishing the book's challenge or detracting from the pleasure-giving nuggets it contains.



Binding Type: Paperback
Publisher: Dover Publications
Published: 06/01/1964
ISBN: 9780486210964
Pages: 368
Weight: 0.90lbs
Size: 8.50h x 5.40w x 0.78d
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SKU: 86349818475

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Mark
Chelsea, US
★★★★★ 5
Total GAME CHANGER - incredibly effective toothbrush for dogs
Color: Clear (2-pack)
This silicon finger brush is incredibly easy to use - and so EFFECTIVE (more on that in the last paragraph this review). At first, it seemed a little hard to get on my finger but I simply got my finger wet first under the faucet and it slipped right on with virtually no effort. And once on, it's easy to take off but doesn't slip off accidentally when in use - so - perfect! Quick & simply to clean - rinses off in the sink in seconds, and ready to use the next time. And, my dog not only lets me clean her teeth - she actually like it (this from a dog who used to hate it when I would try to brush her teeth with a regular doggy toothbrush). This silicon "brush" is incredibly maneuverable - way more so than standard dog toothbrushes or regular finger brushes. So much so it makes it super easy to not only get those normally impossible to reach back molars - AND - even the back sides of the teeth! With a normal dog tooth brush (or finger brush) my dog's clamping down made that impossible. Now, it's not only possible - it's easy! Our dog's canine teeth had build-up but it was not until I pulled her gums back and looked at her back molars that I saw how bad things had gotten - and we have a young dog! Her back molars not only had build-up but some appeared to be stained a tea colored brown that did not come off with my fingernail. It was pretty disheartening and I felt terrible. How could this happen so quickly? The vet said it was plaque (and not yet tartar) and that it wasn't bad enough to warrant a professional cleaning - yet - but that I needed to do a better job brushing. He said: "I can see exactly where your brushing stops" (referring to the condition on the back molars which I had not been able to do with a regular brush as my dog just wasn't having it). Tips: here's what's working for us. Instead of squeezing out a pea sized blog of tooth paste onto this brush, I put a tiny dab - that it's - on the very tip of the brush and focus my efforts on two of our dog's worst teeth on one side - on top and then on the bottom. Then I put another small dab and repeat on the other side of her mouth with 4 teeth on that side. Then, I use another small dab and focus work on another group of teeth. All totaled, I'm using maybe 4 to 6 very small dabs of dog toothpaste, probably half the size of pea collectively, perhaps less. That's it. However much you choose to use is up to you - be sure and use an amount that's safe and effective for your dog. Effectiveness: this works and it works well! In just 3 days using the same vanilla flavored enzymatic toothpaste by CET I was seeing improvement. By day 7, that improvement was so obvious I was actually surprised by how much better they looked. It's now been a little over two weeks and they are looking considerably better! Conservatively, I'm thinking a 50% improvement. Not bad for just 2 weeks, right? I'm actually think I'm going to be able to completely reverse things - we'll see. I'll try and update this review again in a few weeks and let you know how it's looking but in the meantime, I am absolutely thrilled with this brush. I paid $16 and it came 2 in a pack) and the first (and only one) I've been using still looks brand new after it's rinsed off. All in all - this brush is a game changer! I can now brush our dogs back teeth and even the back sides of her teeth, all in less than a couple minutes a day.
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Reviewed in the United States on August 23, 2020
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JONNA S. Delp
Louisville, US
★★★★★ 3
Plastic not a brush
Color: Clear (4-pack)
Love the idea, dont care for the texture. It would be nice if they were soft brush and not plastic. Would retuen but i missed the window.
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Reviewed in the United States on May 22, 2026
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Belle7RN
Louisville, US
★★★★★ 5
Better than a toothbrush!
Color: Blue (2-pack)
Perfect for brushing my doggies teeth! Easy to use and my dogs like it better than a toothbrush.
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Reviewed in the United States on June 2, 2026
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Mica
Cuba, US
★★★★★ 5
Great dog toothbrush!
Color: Blue (2-pack)
I’ve been using this product for a year now, and it’s been working great. When paired with vanilla mint enzymatic toothpaste, it effectively cleans my Pomsky’s teeth, including the back teeth. As a result, my fur baby’s teeth remain as white as ever!
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Reviewed in the United States on May 27, 2026
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Kindle Customer Raygin
Dallas, US
★★★★★ 5
Good for those in-between grooming visits
Easy to use, thick, soft and smells wonderful. Keeps the fur babies fresh. Price is right 👍.
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Reviewed in the United States on May 9, 2026

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