A023950 Expansion of 1/((1-x)(1-6x)(1-7x)(1-9x)).

1, 23, 348, 4378, 49679, 528381, 5380306, 53132816, 513181317, 4875626899, 45752166824, 425305531014, 3925114125115, 36023250380777, 329183853207102, 2998041099306172, 27233460168740273, 246879085434889215

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Index entries for linear recurrences with constant coefficients, signature (23,-181,537,-378).

Formula

a(n) = (5*9^(n+3)-20*7^(n+3)+16*6^(n+3)-1)/240. [Yahia Kahloune, May 25 2013]

a(0)=1, a(1)=23, a(2)=348, a(3)=4378; for n>3, a(n) = 23*a(n-1) -181*a(n-2) +537*a(n-3) -378*a(n-4). - Vincenzo Librandi, Jul 12 2013

Mathematica

CoefficientList[Series[1 / ((1 - x) (1 - 6 x) (1 - 7 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 12 2013 *)

Prog

(Magma) I:=[1, 23, 348, 4378]; [n le 4 select I[n] else 23*Self(n-1)-181*Self(n-2)+537*Self(n-3)-378*Self(n-4): n in [1..25]]; /* or */ m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-6*x)*(1-7*x)*(1-9*x)))); // Vincenzo Librandi, Jul 12 2013

Crossrefs

Sequence in context: A025976 A025989 A125480 * A268465 A025973 A277833

Adjacent sequences: A023947 A023948 A023949 * A023951 A023952 A023953

Keyword

nonn,easy

Author

N. J. A. Sloane.

Status

approved