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A209405 G.f.: 1/(1-x) = Sum_{n>=0} a(n)*x^n*Product_{k=1..n+1} (1-x^k). 1
1, 2, 3, 6, 8, 15, 21, 34, 47, 74, 99, 151, 201, 287, 383, 540, 701, 970, 1255, 1688, 2171, 2882, 3657, 4801, 6058, 7819, 9816, 12566, 15619, 19826, 24540, 30812, 37950, 47319, 57901, 71769, 87435, 107525, 130482, 159660, 192721, 234633, 282240, 341656, 409549 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..44.

EXAMPLE

G.f.: 1/(1-x) = 1*(1-x) + 2*x*(1-x)*(1-x^2) + 3*x^2*(1-x)*(1-x^2)*(1-x^3) + 6*x^3*(1-x)*(1-x^2)*(1-x^3)*(1-x^4) + 8*x^4*(1-x)*(1-x^2)*(1-x^3)*(1-x^4)*(1-x^5) +...

PROG

(PARI) {a(n)=local(A=[1]); for(i=1, n+1, A=concat(A, 0); A[#A]=1-polcoeff(sum(m=1, #A, A[m]*x^m*prod(k=1, m, 1-x^k +x*O(x^#A) )), #A) ); A[n+1]}

for(n=0, 50, print1(a(n), ", "))

CROSSREFS

Cf. A126796.

Sequence in context: A138137 A319758 A129374 * A048809 A300671 A268645

Adjacent sequences:  A209402 A209403 A209404 * A209406 A209407 A209408

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Mar 08 2012

STATUS

approved

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Last modified February 18 21:20 EST 2020. Contains 332028 sequences. (Running on oeis4.)