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Search: id:A081307
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| A081307 |
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G.f.: sum(k=1,n,sum(l=1,k,1/(1-x^l))). |
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+0
3
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| 1, 3, 4, 8, 6, 16, 8, 21, 17, 26, 12, 50, 14, 36, 40, 54, 18, 75, 20, 84, 56, 56, 24, 140, 47, 66, 72, 118, 30, 176, 32, 135, 88, 86, 96, 242, 38, 96, 104, 238, 42, 248, 44, 186, 198, 116, 48, 366, 93, 213, 136, 220
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n) = (n+1)*tau(n)-sigma(n) = (n+1)*A000005(n)-A000203(n). - Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 22 2005
a(n)=Sum_{k, 1<=k<=n} k*A113998(n,k) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Feb 03 2007
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PROGRAM
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(PARI) a(n)=if(n<1, 0, polcoeff(sum(k=1, n, sum(l=1, k, 1/(1-x^l)), x*O(x^n)), n))
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CROSSREFS
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Cf. A094471.
Sequence in context: A125715 A129283 A079787 this_sequence A081543 A105753 A019972
Adjacent sequences: A081304 A081305 A081306 this_sequence A081308 A081309 A081310
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 20 2003
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