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 A213471 #6 Jun 02 2025 08:02:35 %S A213471 793,65425,1940673,43399990,836356119,15103463125,263422708979, %T A213471 4498700185621,75773483221458,1264058518607488,20939915070874170, %U A213471 345057032966423355,5662807472785412683,92633089841621699568 %N A213471 Number of 0..3 arrays of length 2*n+6 with sum less than 3*n in any length 2n subsequence (=less than 50% duty cycle). %C A213471 Row 7 of A213464 %H A213471 R. H. Hardin, <a href="/A213471/b213471.txt">Table of n, a(n) for n = 1..210</a> %e A213471 Some solutions for n=3 %e A213471 ..0....0....2....2....2....0....0....0....0....0....2....2....0....0....2....0 %e A213471 ..0....0....0....0....2....2....0....0....2....0....0....2....2....0....0....0 %e A213471 ..0....2....0....2....0....2....0....0....0....2....0....2....2....0....2....2 %e A213471 ..0....2....0....2....0....2....0....2....2....0....2....2....0....2....0....0 %e A213471 ..2....0....2....0....2....0....2....2....0....0....2....0....0....0....0....0 %e A213471 ..3....1....1....0....0....1....0....0....1....2....0....0....0....1....0....0 %e A213471 ..2....0....0....0....3....0....3....0....0....2....2....2....0....1....1....2 %e A213471 ..0....0....0....3....0....1....3....1....2....0....0....1....2....1....0....2 %e A213471 ..0....0....0....0....1....0....0....0....1....2....0....2....0....1....1....0 %e A213471 ..0....1....2....2....1....3....0....0....0....0....2....0....3....2....2....0 %e A213471 ..0....1....1....1....0....2....2....2....2....0....2....3....2....0....3....1 %e A213471 ..1....1....0....2....3....0....0....1....1....3....0....0....0....3....0....0 %K A213471 nonn %O A213471 1,1 %A A213471 _R. H. Hardin_ Jun 12 2012