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Search: id:A001494
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| A001494 |
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Numbers n such that phi(n) = phi(n+2).
(Formerly M3293 N1328)
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+0
3
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| 4, 7, 8, 10, 26, 32, 70, 74, 122, 146, 308, 314, 386, 512, 554, 572, 626, 635, 728, 794, 842, 910, 914, 1015, 1082, 1226, 1322, 1330, 1346, 1466, 1514, 1608, 1754, 1994, 2132, 2170, 2186, 2306, 2402, 2426, 2474, 2590, 2642, 2695, 2762, 2906, 3242, 3314
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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If p and 2p-1 are odd primes then 2(2p-1) is a solution of the equation. Other terms (7,8,32,70,...) are not of this form.
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
V. L. Klee, Jr., Some remarks on Euler's totient function, Amer. Math. Monthly, 54 (1947), 332.
L. Moser, Some equations involving Euler's totient function, Amer. Math. Monthly, 56 (1949), 22-23.
R. K. Guy, Unsolved Problems Number Theory, Sect. B36.
D. M. Burton, Elementry Number Theory, section 7-2.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
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CROSSREFS
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Cf. A000010, A001274.
Sequence in context: A026316 A091158 A084791 this_sequence A092214 A128373 A080578
Adjacent sequences: A001491 A001492 A001493 this_sequence A001495 A001496 A001497
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Jud McCranie (j.mccranie(AT)comcast.net), Dec 24 1999
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