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,-130,300,-189).
FORMULA
a(n) = (9^(n+3)-2*7^(n+3)+2*3^(n+3)-1)/96. - Yahia Kahloune, May 23 2013
a(0)=1, a(1)=20; for n>1, a(n) = 16*a(n-1) -63*a(n-2) +(3^n - 1)/2. - Vincenzo Librandi, Jul 11 2013
a(0)=1, a(1)=20, a(2)=270, a(3)=3100; for n>3, a(n) = 20*a(n-1) -130*a(n-2) +300*a(n-3) -189*a(n-4). - Vincenzo Librandi, Jul 11 2013
MATHEMATICA
CoefficientList[Series[1 / ((1 -x) (1 - 3 x) (1 - 7 x) (1 - 9 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Jul 11 2013 *)
PROG
(Magma) m:=25; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x)*(1-3*x)*(1-7*x)*(1-9*x)))); /* or */ I:=[1, 20, 270, 3100]; [n le 4 select I[n] else 20*Self(n-1)-130*Self(n-2)+300*Self(n-3)-189*Self(n-4): n in [1..25]]; // Vincenzo Librandi, Jul 11 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved