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 A212475 #6 Jun 02 2025 07:58:33 %S A212475 246,5211,93308,1581686,26242268,430682205,7023308036,114062278982, %T A212475 1847205725100,29854017540652,481755564098784,7764949351300178, %U A212475 125039067197089316,2011992600375317822,32354843213417739992 %N A212475 Number of 0..3 arrays of length 2*n+3 with sum no more than 3*n in any length 2n subsequence (=50% duty cycle). %C A212475 Row 4 of A212471 %H A212475 R. H. Hardin, <a href="/A212475/b212475.txt">Table of n, a(n) for n = 1..210</a> %e A212475 Some solutions for n=3 %e A212475 ..1....2....1....1....3....2....3....2....2....0....0....1....1....1....1....0 %e A212475 ..1....0....0....0....1....1....2....1....1....0....1....1....1....0....1....0 %e A212475 ..0....0....2....1....0....0....3....1....0....0....2....3....0....0....1....2 %e A212475 ..0....0....3....2....2....3....1....0....0....1....1....0....0....2....1....2 %e A212475 ..2....1....0....3....0....0....0....3....0....1....1....2....3....0....3....0 %e A212475 ..0....0....1....0....2....0....0....1....3....2....0....0....1....0....0....1 %e A212475 ..3....2....1....0....0....2....0....1....1....1....0....0....0....1....1....0 %e A212475 ..0....0....0....0....1....3....3....2....1....0....2....2....2....2....1....3 %e A212475 ..3....3....3....3....1....0....2....1....1....0....3....1....2....2....3....3 %K A212475 nonn %O A212475 1,1 %A A212475 _R. H. Hardin_ May 17 2012