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 A195250 #7 Jul 22 2025 12:42:32 %S A195250 1024,59049,190514,357847,533142,709613,886084,1062555,1239026, %T A195250 1415497,1591968,1768439,1944910,2121381,2297852,2474323,2650794, %U A195250 2827265,3003736,3180207,3356678,3533149,3709620,3886091,4062562,4239033,4415504,4591975 %N A195250 Number of lower triangles of a 4X4 0..n array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by two or less. %C A195250 Row 4 of A195248 %H A195250 R. H. Hardin, <a href="/A195250/b195250.txt">Table of n, a(n) for n = 1..200</a> %F A195250 Empirical: a(n) = 176471*n - 349213 for n>4 %e A195250 Some solutions for n=5 %e A195250 ..2........5........3........0........5........1........2........3 %e A195250 ..0.0......4.3......2.1......0.2......5.5......0.0......0.2......1.2 %e A195250 ..1.2.1....4.3.1....0.2.2....0.1.3....5.5.3....0.2.1....1.1.1....2.0.2 %e A195250 ..2.1.3.2..3.3.1.0..1.0.1.2..0.2.2.2..4.4.5.4..0.1.0.0..2.0.1.2..2.0.1.0 %K A195250 nonn %O A195250 1,1 %A A195250 _R. H. Hardin_ Sep 13 2011