A047832 Number of self-complementary binary relations on a 2n-element set.

2, 36, 5600, 11220000, 293293716992, 102484848265030656, 491247277315343649710080, 32966971058719932671168222859264, 31464896751148469761776612436741418123264, 432450241375084625203842385525712986695638650716160

Offset: 1

Author

Vladeta Jovovic

Keywords

• nonn
• nice

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..40
• D. Wille, Enumeration of self-complementary structures, J. Comb. Theory B 25 (1978) 143-150.

Crossrefs

Cf. A000171.

Programs

Mathematica

Needs["Combinatorica`"]; Table[ Print[an = GraphPolynomial[4*n + 1, x] /. x -> -1]; an, {n, 1, 9}] (* Jean-François Alcover, Aug 12 2013 *)

Formula

a(n) = A000171(4*n+1).

Extensions

Terms a(10) and beyond from Andrew Howroyd, Sep 17 2018