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 A212238 #11 Sep 07 2025 12:21:22 %S A212238 353,4663,51440,514687,4931630,46305966,429886243,3962696059, %T A212238 36354382954,332393767866,3031533285381,27595759169532, %U A212238 250826014161861,2277103688384513,20652344756363304,187156724402029627,1694914205955775462,15340549508692418292,138778053213558014181 %N A212238 Number of 0..2 arrays of length 5+2*n with sum no more than 2*n in any length 2n subsequence (=50% duty cycle). %H A212238 R. H. Hardin, <a href="/A212238/b212238.txt">Table of n, a(n) for n = 1..210</a> %e A212238 Some solutions for n=3: %e A212238 ..1....2....0....0....1....1....1....2....1....2....0....2....1....2....1....1 %e A212238 ..1....0....2....1....0....0....1....0....2....1....0....0....1....2....0....2 %e A212238 ..0....0....0....0....2....1....1....0....0....1....1....1....1....1....2....1 %e A212238 ..0....0....1....1....0....1....0....0....0....0....2....1....0....0....1....0 %e A212238 ..1....0....0....1....2....1....2....1....0....2....0....0....0....0....0....1 %e A212238 ..1....0....2....0....0....1....1....0....2....0....0....0....0....0....0....1 %e A212238 ..0....0....0....0....0....0....0....2....0....0....0....1....2....0....0....1 %e A212238 ..0....0....2....2....0....1....0....2....0....1....1....1....0....1....2....1 %e A212238 ..1....0....0....0....0....1....1....1....1....2....0....0....1....2....1....0 %e A212238 ..0....2....2....2....0....1....2....0....0....1....1....1....1....2....0....0 %e A212238 ..1....2....0....2....0....0....0....1....1....0....1....2....1....0....2....0 %Y A212238 Row 6 of A212232. %K A212238 nonn,changed %O A212238 1,1 %A A212238 _R. H. Hardin_, May 06 2012