OFFSET
0,2
FORMULA
a(n) ~ 3^(3*n + 13/2) / (832*Pi*n). - Vaclav Kotesovec, Apr 04 2019
MATHEMATICA
Table[Sum[Sum[Sum[(i+j+k)!/(i!*j!*k!), {i, 1, j}], {j, 1, k}], {k, 1, n}], {n, 0, 20}] (* Vaclav Kotesovec, Apr 04 2019 *)
PROG
(PARI) {a(n) = sum(i=1, n, sum(j=i, n, sum(k=j, n, (i+j+k)!/(i!*j!*k!))))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Apr 03 2019
STATUS
approved