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 A247596 #41 May 24 2018 15:56:18 %S A247596 1,5,35,410,6178,122038,2921607,81609320,2588949454,91699869557, %T A247596 3582942335285,153048366545566,7096576775166579,355120233277118103, %U A247596 19084972486216897560,1096965038775477639368,67192642484367187943761,4372413334294007638726854 %N A247596 Number of nonisomorphic binary n X n matrices with three 1's per column under row and column permutations. %H A247596 Andrew Howroyd, <a href="/A247596/b247596.txt">Table of n, a(n) for n = 3..40</a> %H A247596 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 A247596 seq(matrix_marks(n,3), n=3..15); # Using the uploaded program to A247417 %o A247596 (PARI) \\ See A304942 for Blocks %o A247596 a(n) = Blocks(n, n, 3); \\ _Andrew Howroyd_, May 23 2018 %Y A247596 Column k=3 of A304942. %Y A247596 A diagonal of A305027. %Y A247596 Cf. A247417, A247597, A247598. %K A247596 nonn %O A247596 3,2 %A A247596 _Marko Riedel_, Sep 21 2014 %E A247596 Terms a(17) and beyond from _Andrew Howroyd_, May 23 2018