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 A221626 #6 Jul 23 2025 02:04:07 %S A221626 1,5,453,85035,51149685,57614883627,130516916069715, %T A221626 492362067027383802,3063154239917651379537,28932140956374841410316707, %U A221626 405028623674958829496315433651,8040080740216333451541433497055002 %N A221626 Number of 4Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row. %C A221626 Row 4 of A221623 %H A221626 R. H. Hardin, <a href="/A221626/b221626.txt">Table of n, a(n) for n = 1..13</a> %e A221626 Some solutions for n=3 %e A221626 ..2..3..1....1..3..2....1..2..3....2..3..1....2..1..3....1..2..3....2..3..1 %e A221626 ..2..3..1....2..1..3....1..2..3....1..3..2....3..1..2....1..2..3....2..3..1 %e A221626 ..2..3..1....2..3..1....3..1..2....2..1..3....3..1..2....1..3..2....3..1..2 %e A221626 ..1..3..2....2..3..1....2..1..3....3..1..2....2..3..1....2..1..3....1..3..2 %K A221626 nonn %O A221626 1,2 %A A221626 _R. H. Hardin_ Jan 21 2013