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A321968
a(n) = 2^n*n!*[x^n] -sqrt(exp(LambertW(-x)))*(LambertW(-x) + 1).
0
-1, 3, 7, 55, 735, 13851, 336743, 10024911, 353109375, 14361853555, 662358958599, 34154042002983, 1947046027041503, 121593475341796875, 8255204941334951655, 605377094064557529151, 47687467918910168180223, 4015909348423983176411619
OFFSET
0,2
MAPLE
-sqrt(exp(LambertW(-x)))*(LambertW(-x) + 1): series(%, x, 32):
seq(2^n*n!*coeff(%, x, n), n=0..17);
MATHEMATICA
a[n_] := 2^n n! SeriesCoefficient[-Sqrt[Exp[ProductLog[-x]]] (ProductLog[ -x ] + 1), {x, 0, n}]; Table[a[n], {n, 0, 17}] (* Jean-François Alcover, Jul 21 2019 *)
CROSSREFS
Cf. A085527.
Sequence in context: A144030 A228490 A130294 * A100772 A320724 A259266
KEYWORD
sign
AUTHOR
Peter Luschny, Dec 07 2018
STATUS
approved