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 A305027 #7 May 24 2018 08:05:16 %S A305027 1,1,1,1,1,1,1,1,2,1,1,1,3,3,1,1,1,4,7,5,1,1,1,4,11,17,6,1,1,1,4,14, %T A305027 40,35,9,1,1,1,4,15,62,122,76,11,1,1,1,4,16,78,272,410,149,15,1,1,1,4, %U A305027 16,87,427,1307,1270,291,18,1,1,1,4,16,91,544,2754,6178,3888,539,23,1 %N A305027 Array read by antidiagonals: T(n,m) is the number of nonisomorphic binary n X m matrices with 3 1's per column under row and column permutations (m >= 3). %C A305027 Also, the number of pure 2-complexes on m nodes with n multiple 2-simplexes. %H A305027 StackExchange, <a href="http://math.stackexchange.com/questions/616834/">How many arrays with crossed cells, order of rows/columns irrelevant</a>, Dec 13 2013 %e A305027 Array begins: %e A305027 ======================================================== %e A305027 n\m| 3 4 5 6 7 8 9 10 11 %e A305027 ---+---------------------------------------------------- %e A305027 0 | 1 1 1 1 1 1 1 1 1 ... %e A305027 1 | 1 1 1 1 1 1 1 1 1 ... %e A305027 2 | 1 2 3 4 4 4 4 4 4 ... %e A305027 3 | 1 3 7 11 14 15 16 16 16 ... %e A305027 4 | 1 5 17 40 62 78 87 91 92 ... %e A305027 5 | 1 6 35 122 272 427 544 606 635 ... %e A305027 6 | 1 9 76 410 1307 2754 4251 5343 5939 ... %e A305027 7 | 1 11 149 1270 6178 18247 36455 54621 67609 ... %e A305027 8 | 1 15 291 3888 28687 122038 327774 616020 891831 ... %e A305027 ... %o A305027 (PARI) \\ See A304942 for Blocks %o A305027 for(n=1, 8, for(m=3, 11, print1(Blocks(n, m, 3), ", ")); print) %Y A305027 Columns m=4..7 are A001400, A014395, A050911, A050912. %Y A305027 A diagonal is A247596. %Y A305027 Cf. A050913 (infinite m), A304942. %K A305027 nonn,tabl %O A305027 0,9 %A A305027 _Andrew Howroyd_, May 24 2018