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A091287
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Integer solutions x to (sigma[x]+sigma[x+1])/sigma[x+x+1], where sigma[]=A000203.
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6
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1, 4, 215, 646, 923, 944, 1096, 1715, 2379, 5355, 16174, 22891, 38429, 64672, 87584, 110483, 212795, 291039, 353110, 468970, 515698, 733570, 1016519, 1051644, 1198139, 1317343, 1633213, 1735288, 2026945, 2093506, 2709542, 2729979
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OFFSET
| 1,2
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EXAMPLE
| n=215, sigma[215]+sigma[216]=264+600= 2.432=2.sigma[215+216]=sigma[431].
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MATHEMATICA
| Do[s=(DivisorSigma[1, n]+DivisorSigma[1, n+1])/ DivisorSigma[1, 2*n+1]; If[IntegerQ[s], Print[n]], {n, 1, 10000000}]
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CROSSREFS
| Cf. A000203, A067171, A091290.
Sequence in context: A081787 A038790 A042325 * A055627 A167888 A036740
Adjacent sequences: A091284 A091285 A091286 * A091288 A091289 A091290
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Feb 16 2004
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