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Number of self-complementary binary relations on a 2n-element set.
7

%I #16 Dec 03 2018 06:23:58

%S 2,36,5600,11220000,293293716992,102484848265030656,

%T 491247277315343649710080,32966971058719932671168222859264,

%U 31464896751148469761776612436741418123264,432450241375084625203842385525712986695638650716160

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

%H Andrew Howroyd, <a href="/A047832/b047832.txt">Table of n, a(n) for n = 1..40</a>

%H D. Wille, <a href="https://doi.org/10.1016/0095-8956(78)90034-5">Enumeration of self-complementary structures</a>, J. Comb. Theory B 25 (1978) 143-150.

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

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

%Y Cf. A000171.

%K nonn,nice

%O 1,1

%A _Vladeta Jovovic_

%E Terms a(10) and beyond from _Andrew Howroyd_, Sep 17 2018