A021864 - OEIS

%I #14 Jun 13 2015 00:48:56

%S 1,21,294,3466,37275,379407,3727648,35761572,337430709,3146261833,

%T 29083452762,267126341118,2441786303503,22239710844099,

%U 202003194298836,1830950757258904,16569016601938857,149754390830203005

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

%H Harvey P. Dale, <a href="/A021864/b021864.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (21, -147, 379, -252).

%F 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

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

%t 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 *)

%K nonn

%O 0,2

%A _N. J. A. Sloane_.