A087114 Number of regular bipartite simple graphs on n nodes.

1, 1, 2, 1, 3, 1, 4, 1, 6, 1, 8, 1, 18, 1, 40, 1, 230, 1, 4296, 1, 431206, 1, 162267272, 1, 201636689771, 1, 777816803942186, 1, 9865957936943931964, 1, 395886667549681689591841, 1, 53716176608076643470621234239, 1, 23524515269630339982914646821899537, 1, 35682168849414944013547274452501768506834, 1

Offset

0,3

Comments

A graph must be regular and bipartite to be a semisymmetric graph.

Links

Table of n, a(n) for n=0..37.

Eric Weisstein's World of Mathematics, Semisymmetric Graph

Formula

a(2*n + 1) = 1, a(2*n) = A008324(n). - Andrew Howroyd, Sep 05 2018

Crossrefs

Cf. A008323, A008324, A008327.

Sequence in context: A362554 A361441 A340088 * A303753 A088242 A228814

Adjacent sequences: A087111 A087112 A087113 * A087115 A087116 A087117

Keyword

nonn

Author

Eric W. Weisstein, Aug 13 2003

Extensions

a(10)-a(19) from Andrew Howroyd, Sep 05 2018

a(0)=1 prepended and a(20) onwards added by Andrew Howroyd, Feb 21 2024

Status

approved