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Search: id:A069153
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| 0, 1, 3, 7, 10, 19, 21, 35, 39, 56, 55, 91, 78, 113, 118, 155, 136, 208, 171, 252, 234, 287, 253, 395, 310, 404, 390, 497, 406, 614, 465, 651, 586, 698, 626, 910, 666, 875, 822, 1060, 820, 1202, 903, 1239, 1144, 1289, 1081, 1643, 1197, 1581, 1414, 1736
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Inverse Mobius transform of A000217. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 19 2009]
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FORMULA
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G.f.: Sum_{k>0} x^(2*k)/(1-x^k)^3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Dec 17 2002
Row sums of triangle A134840 - Gary W. Adamson (qntmpkt(AT)yahoo.com), Nov 12 2007
G.f. A(x) = (1/2) * x * d/dx log( B(x) ) where B() is g.f. for A052847. - Michael Somos Feb 12 2008
G.f.: Sum_{k>0} ((k^2 - k) / 2) * x^k / (1 - x^k). - Michael Somos Feb 12 2008
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EXAMPLE
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x^2 + 3*x^3 + 7*x^4 + 10*x^5 + 19*x^6 + 21*x^7 + 35*x^8 + 39*x^9 + 56*x^10 + ...
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PROGRAM
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(PARI) {a(n) = if( n<1, 0, sumdiv(n, d, d^2 - d) / 2)}
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CROSSREFS
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Cf. A007437.
Cf. A134840.
Sequence in context: A042591 A098001 A024330 this_sequence A167390 A000223 A031328
Adjacent sequences: A069150 A069151 A069152 this_sequence A069154 A069155 A069156
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KEYWORD
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easy,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 08 2002
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