A035483 Number of 2n X 2n symmetric matrices whose first row is 1..2n and whose rows and columns are all permutations of 1..2n.

1, 1, 4, 456, 10936320, 130025295912960, 2209617218725251404267520

Offset: 0

Author

Joshua Zucker and Joe Keane

Keywords

• more
• nonn
• nice

Crossrefs

Cf. A000438, A035481, A000315, A002860, A003090, A040082.

Formula

a(n) = A035481(2*n). - Max Alekseyev, Apr 23 2010

Extensions

a(5)-a(6) from Ian Wanless, Oct 20 2019