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 A212239 #6 Apr 23 2021 11:38:51 %S A212239 793,11518,131950,1376128,13468524,128148456,1200645159,11143104246, %T A212239 102770036310,943639250739,8636456931969,78848824010001, %U A212239 718489851092745,6537040547889223,59402114237433426,539234176052230974 %N A212239 Number of 0..2 arrays of length 6+2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle). %C A212239 Row 7 of A212232. %H A212239 R. H. Hardin, <a href="/A212239/b212239.txt">Table of n, a(n) for n = 1..210</a> %e A212239 Some solutions for n=3 %e A212239 ..1....0....2....1....1....1....0....0....1....0....1....0....0....1....1....1 %e A212239 ..0....1....0....0....0....2....0....2....1....0....1....0....0....1....0....2 %e A212239 ..2....1....0....0....2....0....0....2....0....0....0....2....1....2....0....0 %e A212239 ..0....0....0....0....1....2....1....0....0....1....1....1....2....0....0....2 %e A212239 ..1....0....0....0....1....1....2....1....1....0....2....2....1....2....1....0 %e A212239 ..1....1....0....0....1....0....1....0....0....2....0....1....0....0....0....1 %e A212239 ..2....0....0....0....0....1....0....0....0....0....0....0....0....0....0....0 %e A212239 ..0....0....0....0....1....0....0....2....2....0....2....0....0....0....1....1 %e A212239 ..1....0....1....2....1....0....2....0....0....0....0....2....0....1....0....1 %e A212239 ..0....1....0....0....1....1....1....0....0....2....1....0....0....1....2....1 %e A212239 ..0....1....1....2....1....0....1....2....0....1....1....1....2....1....1....2 %e A212239 ..0....0....1....1....0....2....1....0....1....0....1....2....0....0....2....0 %Y A212239 Cf. A212232. %K A212239 nonn %O A212239 1,1 %A A212239 _R. H. Hardin_ May 06 2012