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 A212477 #6 Jun 02 2025 07:58:47 %S A212477 2037,53553,1098260,19960518,344305566,5795798788,96239314549, %T A212477 1584499716270,25938577854660,422900154613448,6874291237701437, %U A212477 111487268294929274,1804868382278013414,29177249831017201248 %N A212477 Number of 0..3 arrays of length 2*n+5 with sum no more than 3*n in any length 2n subsequence (=50% duty cycle). %C A212477 Row 6 of A212471 %H A212477 R. H. Hardin, <a href="/A212477/b212477.txt">Table of n, a(n) for n = 1..210</a> %e A212477 Some solutions for n=3 %e A212477 ..2....0....2....0....2....0....0....2....2....2....2....0....0....0....2....0 %e A212477 ..2....2....0....2....0....0....0....0....0....0....0....0....0....2....0....0 %e A212477 ..0....0....0....2....0....2....0....0....0....2....0....0....2....2....0....2 %e A212477 ..0....2....2....2....2....0....2....2....0....0....2....2....0....2....2....2 %e A212477 ..1....1....0....3....2....1....1....3....0....3....2....2....3....1....1....0 %e A212477 ..2....1....2....0....1....1....2....2....0....0....0....0....0....0....3....0 %e A212477 ..2....2....0....0....2....2....1....0....1....0....2....1....0....0....1....1 %e A212477 ..2....1....2....2....0....1....0....2....1....1....1....3....2....3....0....1 %e A212477 ..0....1....1....1....0....1....2....0....2....1....0....0....3....1....2....0 %e A212477 ..2....1....1....2....3....3....0....0....2....1....2....1....1....2....0....0 %e A212477 ..1....3....2....1....2....1....1....1....0....1....0....1....3....2....1....3 %K A212477 nonn %O A212477 1,1 %A A212477 _R. H. Hardin_ May 17 2012