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 A213468 #6 Jun 02 2025 08:02:13 %S A213468 70,2735,58898,1091036,19105020,325333429,5451265872,90406374528, %T A213468 1488870622780,24396922947484,398282413965566,6483402596528564, %U A213468 105301980143117156,1707201970861977822,27637076220888829232 %N A213468 Number of 0..3 arrays of length 2*n+3 with sum less than 3*n in any length 2n subsequence (=less than 50% duty cycle). %C A213468 Row 4 of A213464 %H A213468 R. H. Hardin, <a href="/A213468/b213468.txt">Table of n, a(n) for n = 1..210</a> %e A213468 Some solutions for n=3 %e A213468 ..0....2....2....1....0....2....0....0....3....1....1....0....0....0....1....3 %e A213468 ..2....3....2....0....0....0....2....2....1....2....3....0....2....2....3....1 %e A213468 ..1....1....0....3....2....1....1....1....1....3....0....0....0....2....3....0 %e A213468 ..0....2....0....0....0....2....2....2....0....0....1....2....0....0....0....0 %e A213468 ..0....0....0....0....0....1....0....0....0....0....1....1....0....0....1....2 %e A213468 ..2....0....3....3....0....0....0....2....3....1....2....0....3....2....0....0 %e A213468 ..3....0....0....0....1....0....1....1....0....0....1....0....2....1....1....1 %e A213468 ..1....3....0....1....2....2....3....2....3....0....0....1....0....3....0....0 %e A213468 ..1....0....2....1....3....2....2....1....2....3....0....1....2....2....3....3 %K A213468 nonn %O A213468 1,1 %A A213468 _R. H. Hardin_ Jun 12 2012