OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (20,-122,268,-165).
FORMULA
a(0)=1, a(1)=20; for n>1, a(n) = 16*a(n-1) -55*a(n-2) +(3^n-1)/2. - Vincenzo Librandi, Jul 10 2013
a(0)=1, a(1)=20, a(2)=278, a(3)=3388; for n>3, a(n) = 20*a(n-1) -122*a(n-2) +268*a(n-3) -165*a(n-4). - Vincenzo Librandi, Jul 10 2013
a(n) = (11^(n+3) - 10*5^(n+3) + 15*3^(n+3) - 6)/480. [Yahia Kahloune, Sep 16 2013]
MATHEMATICA
CoefficientList[Series[1/((1-x)(1-3x)(1-5x)(1-11x)), {x, 0, 20}], x] (* Harvey P. Dale, Apr 02 2011 *)
PROG
(Magma) m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-3*x)*(1-5*x)*(1-11*x)))); /* or */ I:=[1, 20, 278, 3388]; [n le 4 select I[n] else 20*Self(n-1)-122*Self(n-2)+268*Self(n-3)-165*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Jul 10 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved