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 A247597 #35 May 24 2018 15:58:33 %S A247597 1,7,132,6178,594203,85820809,16341829155,3875736708590, %T A247597 1112175913348040,378860991866916370,151006214911844288232, %U A247597 69600017255860985666964,36729204987785981237238642,22003003913198378660826731007,14851323097928973689736994569534 %N A247597 Number of nonisomorphic binary n X n matrices with four 1's per column under row and column permutations. %H A247597 Andrew Howroyd, <a href="/A247597/b247597.txt">Table of n, a(n) for n = 4..40</a> %H A247597 StackExchange, <a href="http://math.stackexchange.com/questions/616834/">How many arrays with crossed cells, order of rows/columns irrelevant</a>, Dec 13 2013 %p A247597 seq(matrix_marks(n,4), n=3..15); # Using the uploaded program to A247417 %o A247597 (PARI) \\ See A304942 for Blocks %o A247597 a(n) = Blocks(n, n, 4); \\ _Andrew Howroyd_, May 24 2018 %Y A247597 Column k=4 of A304942. %Y A247597 Cf. A247417, A247596, A247598. %K A247597 nonn %O A247597 4,2 %A A247597 _Marko Riedel_, Sep 21 2014 %E A247597 Terms a(16) and beyond from _Andrew Howroyd_, May 24 2018