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 A195234 #9 May 06 2018 11:53:46 %S A195234 1024,3151,5428,7705,9982,12259,14536,16813,19090,21367,23644,25921, %T A195234 28198,30475,32752,35029,37306,39583,41860,44137,46414,48691,50968, %U A195234 53245,55522,57799,60076,62353,64630,66907,69184,71461,73738,76015,78292,80569 %N A195234 Number of lower triangles of a 4 X 4 0..n array with each element differing from all of its diagonal, vertical, antidiagonal and horizontal neighbors by one or less. %C A195234 Row 4 of A195232. %H A195234 R. H. Hardin, <a href="/A195234/b195234.txt">Table of n, a(n) for n = 1..200</a> %F A195234 Empirical: a(n) = 2277*n - 1403 for n>1. %F A195234 Conjectures from _Colin Barker_, May 06 2018: (Start) %F A195234 G.f.: x*(1024 + 1103*x + 150*x^2) / (1 - x)^2. %F A195234 a(n) = 2*a(n-1) - a(n-2) for n>3. %F A195234 (End) %e A195234 Some solutions for n=4: %e A195234 ..4........3........2........0........2........4........3........0 %e A195234 ..3.3......2.2......2.3......1.1......1.1......3.4......2.3......1.1 %e A195234 ..4.3.3....2.3.2....2.2.3....2.1.1....0.1.0....3.3.4....3.3.2....2.1.0 %e A195234 ..3.3.2.3..3.3.2.3..1.2.2.3..1.2.2.2..1.0.0.1..4.4.3.4..2.2.3.3..1.1.1.0 %Y A195234 Cf. A195232. %K A195234 nonn %O A195234 1,1 %A A195234 _R. H. Hardin_, Sep 13 2011