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 A181238 #5 Jul 22 2025 08:38:16 %S A181238 140,49772,33235358,27896484332,26012734507190,25785064658274014, %T A181238 26631749414632177802,28342597507242978860012, %U A181238 30862541359435652055581702,34221243248277031078812700022,38507504930060734566868274154362 %N A181238 Number of (4*n)X4 binary matrices with all row sums equal and all column sums equal. %C A181238 Row 4 of A181236 %H A181238 R. H. Hardin, <a href="/A181238/b181238.txt">Table of n, a(n) for n=1..22</a> %e A181238 Some solutions for 4X4 %e A181238 ..1..1..0..1....1..1..0..0....0..1..0..1....0..1..0..0....1..0..0..1 %e A181238 ..1..0..1..1....0..0..1..1....1..0..0..1....0..0..0..1....1..1..0..0 %e A181238 ..0..1..1..1....1..0..0..1....0..1..1..0....0..0..1..0....0..0..1..1 %e A181238 ..1..1..1..0....0..1..1..0....1..0..1..0....1..0..0..0....0..1..1..0 %K A181238 nonn %O A181238 1,1 %A A181238 _R. H. Hardin_ Oct 10 2010