A021864 Expansion of 1/((1-x)(1-4x)(1-7x)(1-9x)).

1, 21, 294, 3466, 37275, 379407, 3727648, 35761572, 337430709, 3146261833, 29083452762, 267126341118, 2441786303503, 22239710844099, 202003194298836, 1830950757258904, 16569016601938857, 149754390830203005

Offset

0,2

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (21, -147, 379, -252).

Formula

a(n) = 21*a(n-1) - 147*a(n-2) + 379*a(n-3) - 252*a(n-4), with a(0)=1, a(1)=21, a(2)=294, a(3)=3466. - Harvey P. Dale, Feb 01 2013

a(n) = (9^(n+4) - 20*7^(n+3) + 4^(n+5) - 5)/720. [Yahia Kahloune, Jun 26 2013]

Mathematica

CoefficientList[Series[1/((1-x)(1-4x)(1-7x)(1-9x)), {x, 0, 30}], x] (* or *) LinearRecurrence[{21, -147, 379, -252}, {1, 21, 294, 3466}, 30] (* Harvey P. Dale, Feb 01 2013 *)

Crossrefs

Sequence in context: A181381 A081137 A027474 * A020570 A025940 A041844

Adjacent sequences: A021861 A021862 A021863 * A021865 A021866 A021867

Keyword

nonn

Author

N. J. A. Sloane.

Status

approved