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 A183720 #7 Oct 06 2015 22:01:12 %S A183720 0,2,124,14886,3723606,2740758406,5585215240568,33429749952933774, %T A183720 583208471844467888006 %N A183720 1/12 the number of (n+1) X (n+1) 0..5 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease, and at least two adjacent blocks having the same increasing direction. %C A183720 Diagonal of A183729. %e A183720 Some solutions with the first block increasing clockwise for 3 X 3: %e A183720 ..5..0..1....1..2..3....4..5..4....2..3..2....0..1..2....5..0..5....3..4..3 %e A183720 ..4..3..2....0..5..4....3..0..3....1..4..1....5..4..3....4..1..4....2..5..2 %e A183720 ..5..0..1....1..2..3....2..1..2....0..5..0....0..1..2....3..2..3....1..0..1 %e A183720 ... %e A183720 ...R..R.......R..R.......R..L.......R..L.......R..R.......R..L.......R..L... %e A183720 ...L..L.......L..L.......R..L.......R..L.......L..L.......R..L.......R..L... %K A183720 nonn %O A183720 1,2 %A A183720 _R. H. Hardin_, Jan 06 2011