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 A198657 #7 Jul 22 2025 13:03:20 %S A198657 1,14,185,3904,98467,3053286,109133049,4460603630,202661109307, %T A198657 10057569576034,533251017131222,29684104738808241,1708995821028336330, %U A198657 100671800330158890680,6020806089426293935506,363687165160204642974491 %N A198657 Number of nX3 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 A198657 Column 3 of A198661 %H A198657 R. H. Hardin, <a href="/A198657/b198657.txt">Table of n, a(n) for n = 1..138</a> %e A198657 Some solutions with all values 0 to 7 for n=6 %e A198657 ..0..0..1....0..1..1....0..1..1....0..1..2....0..0..1....0..1..1....0..1..1 %e A198657 ..2..2..1....0..2..2....0..0..2....0..1..2....2..2..1....0..2..3....0..2..2 %e A198657 ..3..4..5....3..3..4....3..3..2....3..3..4....3..3..4....0..2..3....3..3..2 %e A198657 ..3..4..5....5..3..4....4..5..6....5..5..4....5..5..4....4..5..5....4..4..5 %e A198657 ..6..6..0....5..6..7....4..5..6....6..6..6....6..6..4....4..6..6....6..5..5 %e A198657 ..7..7..0....6..6..7....4..7..7....7..7..6....7..7..7....7..7..6....6..7..7 %K A198657 nonn %O A198657 1,2 %A A198657 _R. H. Hardin_ Oct 28 2011