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 A301400 #4 Mar 20 2018 11:02:21 %S A301400 0,0,0,0,1,0,0,2,2,0,0,4,3,4,0,0,9,13,13,9,0,0,19,44,78,44,19,0,0,41, %T A301400 156,446,446,156,41,0,0,88,554,2619,4857,2619,554,88,0,0,189,1963, %U A301400 15538,49325,49325,15538,1963,189,0,0,406,6964,92338,521514,885003,521514 %N A301400 T(n,k)=Number of nXk 0..1 arrays with every element equal to 2, 3, 4, 5 or 6 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero. %C A301400 Table starts %C A301400 .0...0....0......0........0..........0............0..............0 %C A301400 .0...1....2......4........9.........19...........41.............88 %C A301400 .0...2....3.....13.......44........156..........554...........1963 %C A301400 .0...4...13.....78......446.......2619........15538..........92338 %C A301400 .0...9...44....446.....4857......49325.......521514........5457161 %C A301400 .0..19..156...2619....49325.....885003.....16325745......299552320 %C A301400 .0..41..554..15538...521514...16325745....528025038....16971131642 %C A301400 .0..88.1963..92338..5457161..299552320..16971131642...956047339302 %C A301400 .0.189.6964.549096.57311190.5507220522.546618326745.53967719265287 %H A301400 R. H. Hardin, <a href="/A301400/b301400.txt">Table of n, a(n) for n = 1..263</a> %F A301400 Empirical for column k: %F A301400 k=1: a(n) = a(n-1) %F A301400 k=2: a(n) = a(n-1) +2*a(n-2) +a(n-3) %F A301400 k=3: [order 15] %F A301400 k=4: [order 45] %e A301400 Some solutions for n=5 k=4 %e A301400 ..0..0..1..1. .0..0..1..1. .0..0..1..1. .0..0..1..1. .0..0..0..0 %e A301400 ..0..0..1..1. .0..0..1..1. .0..1..1..1. .0..0..1..1. .0..0..0..0 %e A301400 ..0..0..1..0. .0..0..1..0. .1..1..0..0. .0..0..0..0. .1..1..0..0 %e A301400 ..0..1..0..0. .0..0..0..0. .1..0..0..1. .0..1..0..0. .1..0..1..1 %e A301400 ..1..1..0..0. .0..0..0..0. .0..0..1..1. .1..1..0..0. .0..0..1..1 %Y A301400 Column 2 is A078039(n-2). %K A301400 nonn,tabl %O A301400 1,8 %A A301400 _R. H. Hardin_, Mar 20 2018