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 A203492 #7 Jul 22 2025 17:17:25 %S A203492 3,10,80,556,3348,20596,134412,888232,5836068,38457456,255381636, %T A203492 1704162724,11399565860,76433483528,513785171540,3461284463632, %U A203492 23360156262164,157908381404144,1068981156413892,7246198178206132 %N A203492 Number of 2Xn 0..2 arrays with row sums equal and column sums unequal to adjacent columns. %C A203492 Row 2 of A203491 %H A203492 R. H. Hardin, <a href="/A203492/b203492.txt">Table of n, a(n) for n = 1..97</a> %e A203492 Some solutions for n=5 %e A203492 ..0..2..0..2..2....1..0..1..2..0....2..1..0..2..1....1..1..1..2..1 %e A203492 ..0..1..2..2..1....2..0..2..0..0....2..2..1..1..0....1..2..1..1..1 %K A203492 nonn %O A203492 1,1 %A A203492 _R. H. Hardin_ Jan 02 2012