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A063986
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Numbers n such that n divides Sum_{k=1..n} A051953(k) where A051953(k)=k-Phi(k). Arithmetic mean of first n cototient values is an integer.
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6
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1, 4, 5, 24, 25, 249, 600, 617, 12272, 13763, 21332, 25228, 783665, 15748051, 41846733, 195853251, 2488541984, 14399065016, 21119309213, 22430204140, 43787603128, 157825075944, 206651865067, 271605149320, 374049315076, 650288309748
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The odd terms of A048290 and A063986 are the same. - Jud McCranie (JudMcCranie(AT)ugaalum.uga.edu), Jun 26 2005
a(27) > 10^12. - Donovan Johnson, Dec 09 2011
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EXAMPLE
| n=5: (1+1+2+2+4)/5 = 2
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MATHEMATICA
| s = 0; Do[s = s + n - EulerPhi[n]; If[ IntegerQ[s/n], Print[n]], {n, 1, 10^7} ]
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CROSSREFS
| Cf. A051953, A000010, A002088, A048920, A000217, A050226.
Sequence in context: A176957 A010302 A171885 * A039583 A042123 A041531
Adjacent sequences: A063983 A063984 A063985 * A063987 A063988 A063989
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Sep 06 2001
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EXTENSIONS
| More terms from Dean Hickerson, Sep 07, 2001
One more term from Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 07 2001
a(16) and a(17) from J. McCranie, Jun 22, 2005.
a(18)-a(21) from Donovan Johnson (donovan.johnson(AT)yahoo.com), May 11 2010
a(22)-a(26) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 09 2011
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