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 A212233 #6 May 04 2021 21:57:44 %S A212233 6,50,435,3834,34001,302615,2699598,24121674,215786649,1932081885, %T A212233 17311097568,155188936431,1391839527240,12487516404434, %U A212233 112071578930795,1006067340461802,9033468257955009,81126883587357557,728697257578499280 %N A212233 Number of 0..2 arrays of length 2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle). %C A212233 Row 1 of A212232. %H A212233 R. H. Hardin, <a href="/A212233/b212233.txt">Table of n, a(n) for n = 1..210</a> %e A212233 Some solutions for n=3 %e A212233 ..2....1....2....1....0....1....1....0....0....0....1....0....1....1....0....0 %e A212233 ..0....0....0....0....2....0....2....2....0....2....1....1....1....0....1....2 %e A212233 ..2....2....0....1....1....2....0....0....1....1....0....2....1....1....1....0 %e A212233 ..1....1....1....1....0....0....1....2....0....0....1....2....0....0....1....0 %e A212233 ..0....0....0....1....2....1....1....1....1....2....1....1....0....1....0....1 %e A212233 ..1....0....1....1....0....1....1....0....2....1....0....0....2....2....1....1 %Y A212233 Cf. A212232. %K A212233 nonn %O A212233 1,1 %A A212233 _R. H. Hardin_ May 06 2012