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 A213465 #6 Jun 02 2025 08:01:53 %S A213465 6,106,1758,28722,466136,7536790,121573668,1957953138,31497261096, %T A213465 506264941416,8132104116670,130559338628190,2095252193645448, %U A213465 33614011364219588,539119053140521448,8644670545679274098 %N A213465 Number of 0..3 arrays of length 2*n with sum less than 3*n in any length 2n subsequence (=less than 50% duty cycle). %C A213465 Row 1 of A213464 %H A213465 R. H. Hardin, <a href="/A213465/b213465.txt">Table of n, a(n) for n = 1..210</a> %e A213465 Some solutions for n=3 %e A213465 ..0....1....2....1....2....1....0....1....3....0....2....1....3....0....3....2 %e A213465 ..2....2....1....2....0....1....2....1....2....2....0....2....0....1....0....0 %e A213465 ..0....1....1....0....0....1....1....0....1....3....2....3....1....3....1....0 %e A213465 ..0....1....1....1....1....2....0....2....0....1....3....1....0....0....3....1 %e A213465 ..0....2....1....2....0....0....3....2....1....2....0....1....0....2....0....2 %e A213465 ..2....1....0....0....3....3....0....2....0....0....0....0....1....2....0....1 %K A213465 nonn %O A213465 1,1 %A A213465 _R. H. Hardin_ Jun 12 2012