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A067171
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Numbers n such that sigma(n+1)+sigma(n)=sigma(2n+1).
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2
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1, 4, 646, 1096, 16174, 22891, 64672, 353110, 468970, 515698, 733570, 1317343, 1633213, 1735288, 2026945, 2093506, 2709542, 4413772, 5005825, 5346241, 5388154, 6134527, 12811666, 15453229, 19063174, 20565214, 22172791, 35476021
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Integer solutions x to (q=sigma[x]+sigma[x+1])/sigma[x+x+1] such that q=1, i.e. sigma[x]+sigma[x+1])=sigma[2x+1]; sigma[]=A000203. - Labos E. (labos(AT)ana.sote.hu), Feb 16 2004
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MATHEMATICA
| Do[s=(DivisorSigma[1, n]+DivisorSigma[1, n+1])/ DivisorSigma[1, 2*n+1]; If[Equal[s, 1], Print[n]], {n, 1, 10000000}] - Labos E. (labos(AT)ana.sote.hu), Feb 16 2004
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CROSSREFS
| Cf. A000203, A091287-A091290.
Sequence in context: A191953 A169619 A091288 * A046348 A183150 A202368
Adjacent sequences: A067168 A067169 A067170 * A067172 A067173 A067174
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 18 2002
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EXTENSIONS
| More terms from Labos E. (labos(AT)ana.sote.hu), Feb 16 2004
Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 02 2008 at the suggestion of R. J. Mathar
a(22)-a(28) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Jan 31 2009
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