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A162640 G.f. is the polynomial (Product_{k=1..20} (1 - x^(3*k)))/(1-x)^20. 1
1, 20, 210, 1539, 8835, 42294, 175559, 648925, 2177361, 6728260, 19363355, 52364721, 134036525, 326685790, 761961825, 1707940096, 3692525360, 7724060310, 15675545395, 30937970105, 59507001114, 111753986081 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

This is a row of the triangle in A162499. Only finitely many terms are nonzero.

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..610

MAPLE

m:=20: seq(coeff(series(mul((1-x^(3*k)), k=1..m)/(1-x)^m, x, n+1), x, n), n=0..21); # Muniru A Asiru, Jul 07 2018

MATHEMATICA

CoefficientList[Series[Times@@Table[1-x^n, {n, 3, 60, 3}]/(1-x)^20, {x, 0, 30}], x] (* Harvey P. Dale, May 06 2012 *)

PROG

(PARI) x='x+O('x^50); A = prod(k=1, 20, (1-x^(3*k)))/(1-x)^20; Vec(A) \\ G. C. Greubel, Jul 06 2018

(MAGMA) m:=50; R<x>:=PowerSeriesRing(Integers(), m); F:=(&*[(1-x^(3*k)): k in [1..20]])/(1-x)^20; Coefficients(R!(F)); // G. C. Greubel, Jul 06 2018

CROSSREFS

Sequence in context: A074668 A139620 A094311 * A060853 A010972 A126905

Adjacent sequences:  A162637 A162638 A162639 * A162641 A162642 A162643

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 02 2009

STATUS

approved

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Last modified September 19 23:31 EDT 2019. Contains 327207 sequences. (Running on oeis4.)