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 A212472 #6 Jun 02 2025 07:58:18 %S A212472 10,150,2338,36814,582440,9240426,146861788,2337014158,37222215640, %T A212472 593246686360,9460081927746,150915638082466,2408347433725048, %U A212472 38443582673708348,613802451466325528,9802073528030277518 %N A212472 Number of 0..3 arrays of length 2*n with sum no more than 3*n in any length 2n subsequence (=50% duty cycle). %C A212472 Row 1 of A212471 %H A212472 R. H. Hardin, <a href="/A212472/b212472.txt">Table of n, a(n) for n = 1..210</a> %e A212472 Some solutions for n=3 %e A212472 ..0....1....2....1....3....1....0....0....1....3....3....1....3....2....1....0 %e A212472 ..3....3....1....0....3....0....1....3....2....0....1....1....3....0....1....3 %e A212472 ..1....2....0....3....1....0....2....0....0....3....1....3....0....0....1....2 %e A212472 ..2....2....3....1....0....3....0....3....0....1....1....0....2....1....2....0 %e A212472 ..0....0....0....1....0....2....1....1....2....0....3....1....0....3....3....0 %e A212472 ..3....0....1....1....2....2....0....2....1....0....0....2....1....3....0....0 %K A212472 nonn %O A212472 1,1 %A A212472 _R. H. Hardin_ May 17 2012