A144575 E,g.f.: exp(1-sqrt(1-2*x-3*x^2)).

1, 1, 5, 25, 217, 2321, 32221, 536425, 10547825, 238451617, 6103391221, 174418724921, 5506024371145, 190282381973425, 7145586497798477, 289733147423281801, 12615792602988127201, 587128127734854278465, 29084008051746449028325, 1527881758843209566647897

Offset

0,3

Links

Table of n, a(n) for n=0..19.

Formula

a(n) ~ 3^(n-1/2)*sqrt(2)*n^(n-1)/exp(n-1). - Vaclav Kotesovec, Jun 02 2013

Conjecture D-finite with recurrence: a(n) +(-2*n+3)*a(n-1) +(-3*n^2+12*n-10)*a(n-2) +3*(-2*n+3)*a(n-3) -9*(n-1)*(n-3)*a(n-4)=0. - R. J. Mathar, Jan 24 2020

Mathematica

With[{nn=20}, CoefficientList[Series[Exp[1-Sqrt[1-2x-3x^2]], {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Mar 26 2013 *)

Crossrefs

Cf. A001515, A144576.

Sequence in context: A080631 A080632 A245166 * A327619 A005452 A061839

Adjacent sequences: A144572 A144573 A144574 * A144576 A144577 A144578

Keyword

nonn

Author

N. J. A. Sloane, Jan 07 2009

Status

approved