OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..100
FORMULA
a(n) ~ -(-1)^n * 3^(3*n + 5/2) / (256*Pi*n). - Vaclav Kotesovec, Apr 04 2019
MATHEMATICA
Table[-Sum[Sum[Sum[(-1)^(i + j + k)*(i + j + k)!/(3!*i!*j!*k!), {i, 1, n}], {j, 1, n}], {k, 1, n}], {n, 0, 17}] (* Amiram Eldar, Apr 03 2019 *)
PROG
(PARI) {a(n) = -sum(i=1, n, sum(j=1, n, sum(k=1, n, (-1)^(i+j+k)*(i+j+k)!/(6*i!*j!*k!))))}
(PARI) {a(n) = -sum(i=3, 3*n, (-1)^i*i!*polcoef(sum(j=1, n, x^j/j!)^3, i))/6} \\ Seiichi Manyama, May 20 2019
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Apr 03 2019
STATUS
approved