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 A212237 #6 Jun 02 2025 07:56:25 %S A212237 157,1895,19834,191853,1804448,16740414,154089343,1411275807, %T A212237 12881812440,117296944044,1066131740757,9676805664696,87736143094569, %U A212237 794774081112347,7194441026799642,65086616352089797,588530376516453384 %N A212237 Number of 0..2 arrays of length 4+2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle). %C A212237 Row 5 of A212232 %H A212237 R. H. Hardin, <a href="/A212237/b212237.txt">Table of n, a(n) for n = 1..210</a> %e A212237 Some solutions for n=3 %e A212237 ..2....0....0....1....0....0....1....0....1....2....1....2....1....0....0....2 %e A212237 ..0....0....2....1....1....1....2....2....1....1....0....0....1....2....1....0 %e A212237 ..1....1....2....0....2....0....1....0....1....0....1....1....0....0....0....0 %e A212237 ..0....1....1....2....0....1....1....2....0....1....2....0....1....0....1....1 %e A212237 ..2....0....0....0....1....2....0....0....1....0....0....0....2....2....1....0 %e A212237 ..1....1....0....1....0....0....0....1....0....0....1....1....1....1....0....1 %e A212237 ..0....2....1....1....1....0....1....1....0....0....1....2....1....0....1....2 %e A212237 ..0....1....0....0....0....1....0....0....1....2....0....0....0....0....0....0 %e A212237 ..0....0....1....2....2....1....1....0....0....0....2....1....0....2....0....2 %e A212237 ..0....0....0....0....0....0....0....2....2....2....2....2....1....1....2....1 %K A212237 nonn %O A212237 1,1 %A A212237 _R. H. Hardin_ May 06 2012