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 A200148 #6 Jul 22 2025 15:41:14 %S A200148 1,3,5,9,15,39,45,129,149,243,369,1365,2061,5901,5951,7785,10519, %T A200148 42519,59473,213561,157559,278835,503513,1553481,1051639,2491707, %U A200148 2981747,6622209,10056593,34139241 %N A200148 Number of 0..2 arrays x(0..n-1) of n elements with zero n-1st difference. %C A200148 Column 2 of A200154 %e A200148 Some solutions for n=6 %e A200148 ..0....0....1....1....2....2....2....1....2....2....2....0....2....0....1....1 %e A200148 ..2....1....0....2....2....0....2....2....1....0....0....0....0....0....0....0 %e A200148 ..1....2....0....0....1....1....2....1....0....0....0....0....2....0....0....1 %e A200148 ..1....2....0....0....0....1....2....0....0....0....1....0....2....1....1....1 %e A200148 ..2....1....0....2....0....0....2....0....1....0....2....0....0....2....2....0 %e A200148 ..0....0....1....1....2....2....2....1....2....2....2....0....2....0....1....1 %K A200148 nonn %O A200148 1,2 %A A200148 _R. H. Hardin_ Nov 13 2011