A032108 Number of reversible strings with n labeled beads of 3 colors.

3, 9, 81, 972, 14580, 262440, 5511240, 132269760, 3571283520, 107138505600, 3535570684800, 127280544652800, 4963941241459200, 208485532141286400, 9381848946357888000, 450328749425178624000

Offset

1,1

Links

Table of n, a(n) for n=1..16.

C. G. Bower, Transforms (2)

Formula

"BIJ" (reversible, indistinct, labeled) transform of 3, 0, 0, 0...

3^n*n!/2 (n>1). E.g.f.: (2-9*x^2)/(2-6*x).

Crossrefs

Sequence in context: A078684 A121858 A215114 * A216206 A038062 A218149

Adjacent sequences: A032105 A032106 A032107 * A032109 A032110 A032111

Keyword

nonn

Author

Christian G. Bower

Status

approved