OFFSET
0,2
COMMENTS
Subsequence of A047486. [Bruno Berselli, Feb 07 2013]
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (20,-150,500,-625).
FORMULA
G.f.: 5*x*(1+20*x+25*x^2)/(1-5*x)^4. - Vincenzo Librandi Feb 07 2013
a(n) = 20*a(n-1) - 150*a(n-2) + 500*a(n-3) - 625*a(n-4). - Vincenzo Librandi, Feb 09 2013
MATHEMATICA
CoefficientList[Series[5 x (1 + 20 x + 25 x^2)/(1-5 x)^4, {x, 0, 30}], x] (* Vincenzo Librandi, Feb 07 2013 *)
LinearRecurrence[{20, -150, 500, -625}, {0, 5, 200, 3375}, 20] (* Harvey P. Dale, Aug 16 2024 *)
PROG
(Magma) [n^3*5^n: n in [0..30]]; // Vincenzo Librandi, Feb 07 2013
(Magma) I:=[0, 5, 200, 3375]; [n le 4 select I[n] else 20*Self(n-1)-150*Self(n-2)+500*Self(n-3)-625*Self(n-4): n in [1..30]]; // Vincenzo Librandi, Feb 09 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Apr 07 2007
STATUS
approved