OFFSET
0,6
COMMENTS
Squares of complementary Bell numbers.
FORMULA
a(n) = A000587(n)^2.
MATHEMATICA
Table[Exp[2] Sum[Sum[(-1)^(i + j) (i j)^n/(i! j!), {j, 0, Infinity}], {i, 0, Infinity}], {n, 0, 22}]
Table[BellB[n, -1]^2, {n, 0, 22}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 12 2020
STATUS
approved