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 A212478 #6 Jun 02 2025 07:58:54 %S A212478 5864,172980,3708268,70600212,1246724695,21292987433,357117150362, %T A212478 5923063781205,97514964737576,1597131825489558,26058934302628094, %U A212478 423954039651724411,6881835973423757103,111509561797692820078 %N A212478 Number of 0..3 arrays of length 2*n+6 with sum no more than 3*n in any length 2n subsequence (=50% duty cycle). %C A212478 Row 7 of A212471 %H A212478 R. H. Hardin, <a href="/A212478/b212478.txt">Table of n, a(n) for n = 1..210</a> %e A212478 Some solutions for n=3 %e A212478 ..0....2....2....0....2....0....0....2....0....0....0....0....0....0....2....2 %e A212478 ..2....0....2....2....2....2....0....0....0....2....0....2....0....0....2....2 %e A212478 ..0....2....0....0....0....2....0....0....2....0....0....2....2....2....0....0 %e A212478 ..0....2....0....0....2....0....0....2....2....0....2....0....0....0....2....0 %e A212478 ..2....2....0....2....0....0....0....0....2....0....2....2....0....2....2....2 %e A212478 ..0....0....0....0....2....2....0....0....0....0....0....2....0....0....0....2 %e A212478 ..0....2....0....0....0....0....2....0....0....3....0....0....1....1....2....0 %e A212478 ..0....0....3....0....3....0....0....3....1....2....2....1....1....3....2....2 %e A212478 ..3....1....3....3....2....3....0....1....0....0....2....0....3....0....1....0 %e A212478 ..1....2....2....1....0....1....0....2....0....1....0....2....2....2....1....3 %e A212478 ..3....2....0....1....0....1....0....0....3....0....0....2....0....1....1....0 %e A212478 ..2....2....0....2....3....1....3....1....0....0....2....3....0....1....2....3 %K A212478 nonn %O A212478 1,1 %A A212478 _R. H. Hardin_ May 17 2012