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A047832 Number of self-complementary binary relations on a 2n-element set. 7
2, 36, 5600, 11220000, 293293716992, 102484848265030656, 491247277315343649710080, 32966971058719932671168222859264, 31464896751148469761776612436741418123264, 432450241375084625203842385525712986695638650716160 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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.

FORMULA

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

MATHEMATICA

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

CROSSREFS

Cf. A000171.

Sequence in context: A319507 A001070 A095229 * A004003 A060739 A333209

Adjacent sequences: A047829 A047830 A047831 * A047833 A047834 A047835

KEYWORD

nonn,nice

AUTHOR

Vladeta Jovovic

EXTENSIONS

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

STATUS

approved

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Last modified December 2 11:09 EST 2022. Contains 358493 sequences. (Running on oeis4.)