%N a(m^2) = m^3; a(m^2+k) = m^3 + km, 0 <= k <= m; a(m(m+1)) = (m+1)m^2; a(m(m+1)+k) = (m+1)m^2 + k(2m+1), 0 <= k <= m+1; a((m+1)^2) = (m+1)^3.
%C A lower bound on A121231(n), the maximal number of 1's in any (0,1)-matrix M such that M^2 is also a (0,1)-matrix.
%C For example, for m^2 x m^2 matrices one can obtain a(m^2) = m^3 using m^2 m x m matrices with one row of m of 1's and (m-1) rows of m of 0's.
%A _Dan Dima_, Aug 24 2006
%E Edited by R. J. Mathar, Oct 01 2008