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 A198902 #7 Jul 22 2025 13:06:31 %S A198902 5,380,50384,6907736,948656912,130292546801,17895005957823, %T A198902 2457786852894234,337564362706067534,46362726246946052884, %U A198902 6367681611531782236418,874568266109492180669275 %N A198902 Number of nX4 0..4 arrays with values 0..4 introduced in row major order and no element equal to any horizontal or vertical neighbor. %C A198902 Column 4 of A198906 %H A198902 R. H. Hardin, <a href="/A198902/b198902.txt">Table of n, a(n) for n = 1..200</a> %F A198902 Empirical: a(n) = 163*a(n-1) -3751*a(n-2) +32097*a(n-3) -120287*a(n-4) +201471*a(n-5) -148296*a(n-6) +38604*a(n-7) %e A198902 Some solutions with values 0 to 4 for n=5 %e A198902 ..0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1....0..1..0..1 %e A198902 ..1..0..1..0....1..0..1..0....1..0..1..0....1..0..1..0....1..0..1..0 %e A198902 ..0..2..3..1....0..2..3..1....0..2..3..1....0..2..0..2....0..2..0..3 %e A198902 ..1..0..4..0....2..3..0..4....1..0..2..0....3..1..2..1....3..0..3..4 %e A198902 ..2..1..0..2....1..2..4..0....4..3..4..2....4..0..1..3....2..3..0..3 %K A198902 nonn %O A198902 1,1 %A A198902 _R. H. Hardin_ Oct 31 2011