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 A198658 #7 Jul 22 2025 13:03:28 %S A198658 2,76,3904,344044,40065880,6046334324,1099981072751,231069206905205, %T A198658 53332894057280732,13062771135606107106,3312119561085281340968, %U A198658 856694689962959996618514,224079649012945587508397744 %N A198658 Number of nX4 0..7 arrays with values 0..7 introduced in row major order and each element equal to at least one horizontal or vertical neighbor. %C A198658 Column 4 of A198661 %H A198658 R. H. Hardin, <a href="/A198658/b198658.txt">Table of n, a(n) for n = 1..17</a> %e A198658 Some solutions with all values 0 to 7 for n=4 %e A198658 ..0..0..1..1....0..0..1..1....0..1..2..2....0..1..2..3....0..1..1..2 %e A198658 ..2..2..3..4....2..2..3..4....0..1..3..3....0..1..2..3....0..3..3..2 %e A198658 ..5..6..3..4....5..5..3..4....4..5..5..6....4..5..6..6....4..5..5..6 %e A198658 ..5..6..7..7....6..6..7..7....4..7..7..6....4..5..7..7....4..7..7..6 %K A198658 nonn %O A198658 1,1 %A A198658 _R. H. Hardin_ Oct 28 2011