OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..214
FORMULA
a(n) ~ exp(1) * n^(2*n - 3/2) / sqrt(Pi). - Vaclav Kotesovec, Dec 15 2018
EXAMPLE
(2/x^2 + 1/x + 0 + x + 2*x^2)^2 = 4/x^4 + 4/x^3 + 1/x^2 + 4/x + 10 + 4*x + x^2 + 4*x^3 + 4*x^4. So a(2) = 10.
MATHEMATICA
a[n_] := If[n==0, 1, Coefficient[Expand[Sum[k*(x^k + x^(-k)), {k, 0, n}]^n], x, 0]]; Array[a, 15, 0] (* Amiram Eldar, Dec 15 2018 *)
PROG
(PARI) {a(n) = polcoeff((sum(k=0, n, k*(x^k+x^(-k))))^n, 0, x)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Dec 15 2018
STATUS
approved