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, -125, 317, -210).
FORMULA
a(n) = (10*7^(n+3)-24*6^(n+3)+15*5^(n+3)-1)/120. - Yahia Kahloune, May 22 2013.
a(0)=1, a(1)=19, a(2)=236, a(3)=2426; for n>3, a(n) = 19*a(n-1) -125*a(n-2) +317*a(n-3) -210*a(n-4). - Vincenzo Librandi, Jul 12 2013
a(0)=1, a(1)=19; for n>1, a(n) = 13*a(n-1) -42*a(n-2) +(5^n-1)/4. - Vincenzo Librandi, Jul 12 2013
MATHEMATICA
CoefficientList[Series[1 / ((1 - x) (1 - 5 x) (1 - 6 x) (1 - 7 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 12 2013 *)
PROG
(Magma) I:=[1, 19, 236, 2426]; [n le 4 select I[n] else 19*Self(n-1)-125*Self(n-2)+317*Self(n-3)-210*Self(n-4): n in [1..25]]; /* or */ m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-5*x)*(1-6*x)*(1-7*x)))); // Vincenzo Librandi, Jul 12 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved