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,-125,250,-144).
FORMULA
a(0)=1, a(1)=20, a(2)=275; a(n)=(3*9^(n+3) - 4*8^(n+3) + 2^(n+5) - 3)/168. [Yahia Kahloune, Jun 21 2013]
a(0)=1, a(1)=20, a(2)=275, a(3)=3250; for n>3, a(n) = 20*a(n-1) -125*a(n-2) +250*a(n-3) -144*a(n-4). - Vincenzo Librandi, Jul 08 2013
a(0)=1, a(1)=20; for n>1, a(n) = 17*a(n-1) -72*a(n-2) +2^n -1. - Vincenzo Librandi, Jul 08 2013
MATHEMATICA
CoefficientList[Series[1 / ((1 - x) (1 - 2 x) (1 - 8 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 08 2013 *)
LinearRecurrence[{20, -125, 250, -144}, {1, 20, 275, 3250}, 20] (* Harvey P. Dale, Mar 04 2019 *)
PROG
(Magma) I:=[1, 20, 275, 3250]; [n le 4 select I[n] else 20*Self(n-1)-125*Self(n-2)+250*Self(n-3)-144*Self(n-4): n in [1..25]]; /* or */ m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-2*x)*(1-8*x)*(1-9*x)))); // Vincenzo Librandi, Jul 08 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved