A104256 [ (2n-1)!!/(4n) ].

0, 0, 1, 6, 47, 433, 4826, 63344, 957206, 16368226, 312484331, 6588211317, 152035645781, 3811750833515, 103171389227156, 2998418499414228, 93127351040630156, 3078376326065274609, 107905191218919625781

Offset

1,4

Comments

Asymptotic estimate for A054499(n).

Links

Table of n, a(n) for n=1..19.

A. Khruzin, Enumeration of chord diagrams

Crossrefs

Sequence in context: A369502 A364748 A365186 * A289211 A307567 A368270

Adjacent sequences: A104253 A104254 A104255 * A104257 A104258 A104259

Keyword

nonn

Author

Ralf Stephan, Mar 02 2005

Status

approved