A025981 Expansion of 1/((1-2*x)*(1-4*x)*(1-9*x)*(1-11*x)).

1, 26, 449, 6526, 86565, 1087242, 13183033, 156056342, 1816137389, 20873693698, 237678368577, 2687080081998, 30211476701173, 338208740115194, 3773239145742281, 41982119790892294, 466091728979229117, 5165604754645852530, 57169014061412059345, 631985411068057076030

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..900

Index entries for linear recurrences with constant coefficients, signature (26,-227,754,-792).

Formula

a(n) = 26*a(n-1) - 227*a(n-2) + 754*a(n-3) - 792*a(n-4), a(0)=1, a(1)=26, a(2)=449, a(3)=6526. - Harvey P. Dale, Aug 11 2012

a(n) = -4*2^n/63 + 32*4^n/35 - 729*9^n/70 + 1331*11^n/126. - R. J. Mathar, Jun 20 2013

a(n) = (4^(n+1)-2^(n+1))/2+20*a(n-1)-99*a(n-2). - Vincenzo Librandi, Jul 02 2026

Mathematica

CoefficientList[Series[1/((1-2x)(1-4x)(1-9x)(1-11x)), {x, 0, 20}], x] (* Harvey P. Dale, Aug 11 2012 *)
(* Alternative: *)
LinearRecurrence[{26, -227, 754, -792}, {1, 26, 449, 6526}, 20] (* Harvey P. Dale, Aug 11 2012 *)

Prog

(Magma) I:=[1, 26]; [n le 2 select I[n] else (4^n-2^n)/2+20*Self(n-1)-99*Self(n-2): n in [1..20]]; // Vincenzo Librandi, Jul 02 2026

Crossrefs

Sequence in context: A024170 A028042 A023956 * A025996 A023540 A025979

Adjacent sequences: A025978 A025979 A025980 * A025982 A025983 A025984

Keyword

nonn,easy

Author

N. J. A. Sloane

Extensions

More terms from Vincenzo Librandi, Jul 02 2026

Status

approved