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 A213467 #6 Jun 02 2025 08:02:06 %S A213467 31,927,18018,319078,5444644,91147915,1508740928,24791568796, %T A213467 405322707108,6602565936460,107259549395070,1738767957760734, %U A213467 28139860212492988,454796793295838938,7342320714558321488 %N A213467 Number of 0..3 arrays of length 2*n+2 with sum less than 3*n in any length 2n subsequence (=less than 50% duty cycle). %C A213467 Row 3 of A213464 %H A213467 R. H. Hardin, <a href="/A213467/b213467.txt">Table of n, a(n) for n = 1..210</a> %e A213467 Some solutions for n=3 %e A213467 ..3....2....1....1....3....0....0....1....0....1....3....0....1....0....3....2 %e A213467 ..0....0....1....0....0....2....0....3....1....2....0....0....0....0....1....1 %e A213467 ..0....1....0....0....0....0....2....0....0....2....1....2....1....0....1....2 %e A213467 ..1....2....1....0....1....2....0....0....3....1....0....2....0....1....0....0 %e A213467 ..0....0....0....1....2....0....2....3....0....1....1....3....1....0....2....2 %e A213467 ..3....2....1....0....1....0....0....0....2....0....3....0....3....1....0....0 %e A213467 ..1....1....1....2....2....2....2....0....1....1....0....0....2....2....0....2 %e A213467 ..1....1....0....3....2....1....0....1....0....3....2....1....0....1....0....0 %K A213467 nonn %O A213467 1,1 %A A213467 _R. H. Hardin_ Jun 12 2012