Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #5 Mar 30 2012 17:40:41
%S 1,5,39,753,25887,1842241,247531775
%N Number of real n X n symmetric (0,1) matrices with nonzero permanent.
%F a(n) = 2^(n(n+1)/2) - A118989(n) = 2^A000217(n) - A118989(n) = A006125(n+1) - A118989(n). [From _Max Alekseyev_, Apr 22 2010]
%Y Cf. A086899, A118989.
%K nonn,more
%O 1,2
%A _Giovanni Resta_, May 08 2006
%E Max Alekseyev's formula corrected (the term 2^(n^2), counting the total number of binary matrices, has been substituted for 2*2^2*...*2^n = 2^(n(n+1)/2), the total number of binary symmetric matrices) by Herman Jamke (hermanjamke(AT)fastmail.fm), Sep 26 2010