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 A200149 #6 Jul 22 2025 15:41:24 %S A200149 1,4,8,22,40,112,182,688,844,2090,2478,21056,20762,112864,113870, %T A200149 204796,141246,2255872,1610768,18946704,15066098,20640826,12378248, %U A200149 332333696,279217826,531539936,618937930,1715570198,330283576,20131457680 %N A200149 Number of 0..3 arrays x(0..n-1) of n elements with zero n-1st difference. %C A200149 Column 3 of A200154 %e A200149 Some solutions for n=6 %e A200149 ..0....1....3....0....3....3....0....2....0....1....0....1....3....3....2....2 %e A200149 ..3....3....1....2....3....3....2....3....3....2....3....3....3....2....3....0 %e A200149 ..3....2....1....3....1....3....0....1....1....3....0....3....1....1....0....2 %e A200149 ..2....2....2....2....1....2....0....1....0....3....0....3....0....0....0....3 %e A200149 ..1....3....3....0....3....1....2....3....1....2....3....3....1....0....3....2 %e A200149 ..0....1....3....0....3....3....0....2....0....1....0....1....3....3....2....2 %K A200149 nonn %O A200149 1,2 %A A200149 _R. H. Hardin_ Nov 13 2011