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 #9 Sep 08 2022 08:45:11
%S 1,21,1147,211965,143331811,366753209781
%N Sum of rank(M) over all n X n matrices over Z with all entries zero or one.
%C The unlikely-looking symbol "+:=" in the MAGMA code is in fact correct. - _N. J. A. Sloane_, Feb 02 2009
%F a(n) = Sum_{k=1..n} k * A064230(n,k). - _Alois P. Heinz_, Jun 18 2022
%o (Magma) for a in [1..5] do b := 0; for c in CartesianPower([0,1], a^2) do b +:= Rank(Matrix(a, a, [aa : aa in c])); end for; print b; end for;
%Y Cf. A064230.
%K hard,more,nonn
%O 1,2
%A Tom Womack (tom(AT)womack.net), Aug 21 2003
%E a(6) from _Alois P. Heinz_, Jun 18 2022