This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A283643 #6 Mar 12 2017 15:11:33
%S A283643 1,0,0,12,0,0,0,0,1330560,0,0,0,0,0,0
%N A283643 The number of n X n real {0,1}-matrices the square of which is the all-ones matrix.
%C A283643 See A283627 for much more information.
%Y A283643 The main entry for this problem is A283627.
%K A283643 nonn
%O A283643 1,4
%A A283643 _N. J. A. Sloane_, Mar 12 2017