| Title: | On the equation $\varphi (|x^m-y^m|)=2^n$ (English) | 
| Author: | Luca, Florian | 
| Language: | English | 
| Journal: | Mathematica Bohemica | 
| ISSN: | 0862-7959 (print) | 
| ISSN: | 2464-7136 (online) | 
| Volume: | 125 | 
| Issue: | 4 | 
| Year: | 2000 | 
| Pages: | 465-479 | 
| Summary lang: | English | 
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| Category: | math | 
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| Summary: | In this paper we investigate the solutions of the equation in the title, where $\phi$ is the Euler function. We first show that it suffices to find the solutions of the above equation when $m=4$ and $x$ and $y$ are coprime positive integers. For this last equation, we show that aside from a few small solutions, all the others are in a one-to-one correspondence with the Fermat primes. (English) | 
| Keyword: | Euler function | 
| Keyword: | Fermat primes | 
| MSC: | 11A25 | 
| MSC: | 11A51 | 
| MSC: | 11A63 | 
| idZBL: | Zbl 0966.11002 | 
| idMR: | MR1802295 | 
| DOI: | 10.21136/MB.2000.126267 | 
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| Date available: | 2009-09-24T21:45:45Z | 
| Last updated: | 2020-07-29 | 
| Stable URL: | http://hdl.handle.net/10338.dmlcz/126267 | 
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| Reference: | [1] R. D. Charmichael: On the numerical factors of arithmetic forms $\alpha^n ± \beta^n$.Ann. Math. 15 (1913-1914), 30-70. | 
| Reference: | [2] F. Luca: Equations involving arithmetic functions of Fibonacci and Lucas numbers.Preprint. To appear in Fibo. Quart. Zbl 0941.11006, MR 1738646 | 
| Reference: | [3] F. Luca: Pascal's triangle and constructible polygons.Preprint, Zbl 1006.11004 | 
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