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A081307 G.f.: Sum_{k=1..n} Sum_{m=1..k} 1/(1-x^m). 4
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; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..52.

FORMULA

a(n) = (n+1)*tau(n) - sigma(n) = (n+1)*A000005(n) - A000203(n). - Vladeta Jovovic, Jan 22 2005

a(n) = Sum_{k=1..n} k*A113998(n,k). - Philippe Deléham, Feb 03 2007

PROG

(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))

CROSSREFS

Cf. A094471.

Sequence in context: A347228 A330575 A079787 * A344225 A081543 A328876

Adjacent sequences:  A081304 A081305 A081306 * A081308 A081309 A081310

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Apr 20 2003

STATUS

approved

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Last modified October 22 18:11 EDT 2021. Contains 348175 sequences. (Running on oeis4.)