A395336 a(n) = n! * [x^n] exp(x)/(2 - x - exp(x)).

1, 3, 14, 95, 858, 9687, 131244, 2074515, 37475342, 761600375, 17197534296, 427167206259, 11574924994554, 339782159979927, 10741567045403060, 363829523464929491, 13144889973459864390, 504597287602912232727, 20509565121841097814000, 879931951523902926816339, 39739108363028638778280050

Offset

0,2

Comments

a(n) is the number of homogeneous linear orderings in n colors (see Gonzalez).

Links

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

David Gonzalez, Enumerative Combinatorics of Homogeneous Linear Orderings, arXiv:2604.14255 [math.CO], 2026. See Theorem 4.8 on pages 11-13.

Mathematica

terms=21; CoefficientList[Series[Exp[x]/(2-x-Exp[x]), {x, 0, terms-1}], x]*Range[0, terms-1]!

Crossrefs

Sequence in context: A005772 A233083 A053984 * A113181 A295105 A392204

Adjacent sequences: A395325 A395326 A395327 * A395337 A395338 A395339

Keyword

nonn

Author

Stefano Spezia, Apr 19 2026

Status

approved