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A144658
a(n) = Sum_{i=1..n} Sum_{j=1..n} Sum_{k=1..n} (i+j+k)!/(i!*j!*k!).
2
0, 6, 222, 5052, 109512, 2432448, 55611294, 1301187912, 30992726652, 748573575780, 18283412752602, 450657126652626, 11192820097106112, 279787295335659972, 7032532241701837758, 177611430241032329568
OFFSET
0,2
LINKS
MATHEMATICA
Table[Sum[Sum[Sum[(i+j+k)!/i!/j!/k!, {i, 1, n}], {j, 1, n}], {k, 1, n}], {n, 1, 30}]
PROG
(PARI) {a(n) = sum(i=1, n, sum(j=1, n, sum(k=1, n, (i+j+k)!/(i!*j!*k!))))} \\ Seiichi Manyama, May 19 2019
(PARI) {a(n) = sum(i=3, 3*n, i!*polcoef(sum(j=1, n, x^j/j!)^3, i))} \\ Seiichi Manyama, May 19 2019
CROSSREFS
Cf. A144511.
Sequence in context: A292692 A015477 A331477 * A203637 A144045 A355669
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 30 2009
STATUS
approved