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 A212476 #6 Jun 02 2025 07:58:40 %S A212476 707,16649,321320,5622580,95010466,1578372444,25966120647, %T A212476 424537002094,6911873593516,112193588288892,1817051683302947, %U A212476 29377851622547612,474335448720482746,7650319463541214660,123278749437509026298 %N A212476 Number of 0..3 arrays of length 2*n+4 with sum no more than 3*n in any length 2n subsequence (=50% duty cycle). %C A212476 Row 5 of A212471 %H A212476 R. H. Hardin, <a href="/A212476/b212476.txt">Table of n, a(n) for n = 1..210</a> %e A212476 Some solutions for n=3 %e A212476 ..2....0....2....2....0....0....0....0....2....0....2....2....0....2....0....0 %e A212476 ..0....2....0....2....2....2....0....2....0....0....0....2....0....2....0....2 %e A212476 ..0....3....1....3....3....2....3....3....2....2....3....0....1....1....0....2 %e A212476 ..3....3....3....2....1....3....1....0....0....2....2....2....2....1....3....0 %e A212476 ..1....0....0....0....0....0....2....1....0....2....0....3....2....0....1....0 %e A212476 ..0....0....0....0....0....0....0....1....1....1....0....0....3....0....1....1 %e A212476 ..0....0....1....0....2....1....0....0....2....0....1....0....0....0....1....1 %e A212476 ..0....3....3....2....1....2....3....3....0....0....2....0....1....2....3....3 %e A212476 ..0....2....1....2....1....3....1....2....0....0....2....3....1....2....0....3 %e A212476 ..1....1....1....3....3....0....3....2....1....0....1....3....1....1....1....0 %K A212476 nonn %O A212476 1,1 %A A212476 _R. H. Hardin_ May 17 2012