OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (19,-113,221,-126).
FORMULA
a(n) = (15*9^(n+3) - 28*7^(n+3) + 48*2^(n+3) - 35)/1680. - Yahia Kahloune, May 19 2013
a(0)=1, a(1)=19, a(2)=248, a(3)=2786; for n>3, a(n) = 19*a(n-1) -113*a(n-2) +221*a(n-3) -126*a(n-4). - Vincenzo Librandi, Jul 08 2013
a(0)=1, a(1)=19; for n>1, a(n) = 16*a(n-1) -63*a(n-2) +2^n -1. - Vincenzo Librandi, Jul 08 2013
MATHEMATICA
CoefficientList[Series[1 / ((1 - x) (1 - 2 x) (1 - 7 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 08 2013 *)
LinearRecurrence[{19, -113, 221, -126}, {1, 19, 248, 2786}, 20]
PROG
(Magma) I:=[1, 19, 248, 2786]; [n le 4 select I[n] else 19*Self(n-1)-113*Self(n-2)+221*Self(n-3)-126*Self(n-4): n in [1..25]]; /* or */ m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-2*x)*(1-7*x)*(1-9*x)))); // Vincenzo Librandi, Jul 08 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved