OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).
FORMULA
a(n) = (n-1) * n * (n+1) * (n+2) * (2*n+1) / 10.
MATHEMATICA
a[n_] := Coefficient[Expand[Sum[k * (x^k + x^(-k)), {k, 0, n}]^3], x, 0]; Array[a, 30, 0] (* Amiram Eldar, Dec 16 2018 *)
Table[((n-1)n(n+1)(n+2)(2n+1))/10, {n, 0, 50}] (* Harvey P. Dale, Jul 01 2019 *)
PROG
(PARI) {a(n) = polcoeff((sum(k=0, n, k*(x^k+x^(-k))))^3, 0, x)}
(PARI) {a(n) = (n-1)*n*(n+1)*(n+2)*(2*n+1)/10}
(GAP) List([0..35], n->(n-1)*n*(n+1)*(n+2)*(2*n+1)/10); # Muniru A Asiru, Dec 16 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 16 2018
STATUS
approved