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 A195274 #7 Jul 22 2025 12:43:18 %S A195274 1,81,39609,119743353,2266745635377,270149651796118149, %T A195274 203368493873412168605037,969036564714736790447759054277 %N A195274 Number of lower triangles of an n X n integer array with each element differing from all of its vertical and horizontal neighbors by 4 or less and triangles differing by a constant counted only once. %C A195274 Column 4 of A195278 %e A195274 Some solutions for n=5 %e A195274 ...0...............0...............0...............0...............0 %e A195274 ...1..4............1..1............1..0............2..5...........-3.-1 %e A195274 ..-1..3..2.........4..3..7.........3..0..4.........1..2..6........-6.-5.-9 %e A195274 ..-4.-1..3..7......3..6.10..7......1..2..0.-3......0..0..2..4.....-6.-7.-8-10 %e A195274 ...0.-3..0..4..2...4..4..8..9..6...0..3..2..1..4..-4.-4.-1..2..2.-10-10.-8-11-13 %K A195274 nonn %O A195274 1,2 %A A195274 _R. H. Hardin_ Sep 14 2011