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 A240644 #6 Jul 23 2025 11:04:25 %S A240644 1,2,6,8,23,60,149,396,1050,2814,7571,20372,54879,147946,399002, %T A240644 1076312,2903613,7833652,21135287,57024772,153859830,415135862, %U A240644 1120101045,3022215348,8154444873,22002086130,59365425382,160178219728,432188727639 %N A240644 Number of nX3 0..1 arrays with no element equal to the same number of vertical neighbors as horizontal neighbors, with new values 0..1 introduced in row major order. %C A240644 Column 3 of A240649 %H A240644 R. H. Hardin, <a href="/A240644/b240644.txt">Table of n, a(n) for n = 1..210</a> %F A240644 Empirical: a(n) = 4*a(n-1) -3*a(n-2) -2*a(n-3) +2*a(n-4) +2*a(n-5) -7*a(n-6) -8*a(n-7) +15*a(n-8) +4*a(n-9) -8*a(n-10) -4*a(n-11) +15*a(n-12) +8*a(n-13) -7*a(n-14) -2*a(n-15) +2*a(n-16) +2*a(n-17) -3*a(n-18) -4*a(n-19) -a(n-20) %e A240644 Some solutions for n=4 %e A240644 ..0..1..0....0..0..0....0..1..0....0..0..0....0..1..0....0..1..0....0..0..0 %e A240644 ..0..1..0....1..0..1....0..1..0....1..1..1....0..1..0....0..1..0....1..0..1 %e A240644 ..1..0..1....1..0..1....0..1..0....0..1..0....1..1..1....0..1..0....1..0..1 %e A240644 ..1..0..1....1..0..1....0..1..0....0..1..0....0..0..0....1..1..1....0..0..0 %K A240644 nonn %O A240644 1,2 %A A240644 _R. H. Hardin_, Apr 09 2014