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 A266570 #5 Aug 12 2016 07:04:21 %S A266570 1,1,5,74,2668,150836,12011058,1279437414,175836809388,30308775142980, %T A266570 6404886614932128 %N A266570 Number of nX2 arrays containing 2 copies of 0..n-1 with no element 1 greater than its northwest or southwest neighbor modulo n and the upper left element equal to 0. %C A266570 Column 2 of A266572. %e A266570 Some solutions for n=6 %e A266570 ..0..4....0..3....0..1....0..3....0..4....0..1....0..0....0..1....0..3....0..1 %e A266570 ..2..2....1..4....5..2....0..5....2..5....5..0....4..5....5..3....0..4....5..3 %e A266570 ..5..0....1..5....4..3....2..2....0..1....4..4....2..1....3..1....5..4....4..2 %e A266570 ..3..3....2..4....5..4....4..5....3..4....5..3....3..4....4..0....2..1....5..3 %e A266570 ..1..1....0..5....2..3....3..4....2..3....3..2....5..2....2..4....5..1....0..1 %e A266570 ..5..4....2..3....0..1....1..1....5..1....2..1....3..1....2..5....3..2....2..4 %Y A266570 Cf. A266572. %K A266570 nonn %O A266570 1,3 %A A266570 _R. H. Hardin_, Jan 01 2016