A320254 a(n) = n! * [x^n] exp(exp(x)*(x + (n/2 - 1)*x^2)).

1, 1, 3, 16, 125, 1291, 16177, 241207, 4153193, 81082225, 1770989921, 42763506919, 1131353484637, 32541516492811, 1011058416700529, 33745374949198231, 1204107124715441873, 45741398365345761073, 1843069565594762478145, 78511973999963036415967, 3525468554804288803649381

Offset

0,3

Comments

For n > 2, a(n) is the n-th term of the exponential transform of n-gonal numbers.

Links

Table of n, a(n) for n=0..20.

N. J. A. Sloane, Transforms

Index to sequences related to polygonal numbers

Mathematica

Table[n! SeriesCoefficient[Exp[Exp[x] (x + (n/2 - 1) x^2)], {x, 0, n}], {n, 0, 20}]

Crossrefs

Cf. A000248, A033462, A279361, A279644, A318118, A318124, A320255.

Sequence in context: A157457 A365626 A000950 * A365627 A245012 A000951

Adjacent sequences: A320251 A320252 A320253 * A320255 A320256 A320257

Keyword

nonn

Author

Ilya Gutkovskiy, Oct 08 2018

Status

approved