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 A297506 #4 Dec 31 2017 07:28:36 %S A297506 1,2,1,4,10,1,7,31,29,1,12,68,110,87,1,21,218,314,531,280,1,37,729, %T A297506 1829,2281,2534,876,1,65,2097,8803,23348,14201,11405,2735,1,114,6139, %U A297506 34757,191192,270845,88808,53175,8583,1,200,18932,157673,1247716,3624914 %N A297506 T(n,k)=Number of nXk 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1 or 2 neighboring 1s. %C A297506 Table starts %C A297506 .1.....2.......4........7.........12...........21.............37 %C A297506 .1....10......31.......68........218..........729...........2097 %C A297506 .1....29.....110......314.......1829.........8803..........34757 %C A297506 .1....87.....531.....2281......23348.......191192........1247716 %C A297506 .1...280....2534....14201.....270845......3624914.......35049871 %C A297506 .1...876...11405....88808....3075264.....66289769......978288822 %C A297506 .1..2735...53175...573119...35919085...1272836591....28914051279 %C A297506 .1..8583..246040..3613793..414559944..23896899569...823340493402 %C A297506 .1.26900.1135117.22999331.4794512057.450529429259.23748019543354 %H A297506 R. H. Hardin, <a href="/A297506/b297506.txt">Table of n, a(n) for n = 1..242</a> %F A297506 Empirical for column k: %F A297506 k=1: a(n) = a(n-1) %F A297506 k=2: a(n) = 2*a(n-1) +2*a(n-2) +5*a(n-3) -a(n-5) -a(n-6) %F A297506 k=3: [order 11] %F A297506 k=4: [order 18] %F A297506 k=5: [order 50] %F A297506 Empirical for row n: %F A297506 n=1: a(n) = 2*a(n-1) -a(n-2) +a(n-3) %F A297506 n=2: a(n) = 3*a(n-1) -2*a(n-2) +9*a(n-3) -6*a(n-4) -8*a(n-5) %F A297506 n=3: [order 10] %F A297506 n=4: [order 24] %F A297506 n=5: [order 59] %e A297506 Some solutions for n=4 k=4 %e A297506 ..1..1..1..1. .0..0..0..0. .0..0..1..0. .1..0..0..0. .0..0..0..0 %e A297506 ..0..0..0..0. .0..0..1..1. .0..0..0..1. .0..1..0..0. .0..0..0..0 %e A297506 ..1..0..0..0. .0..0..0..1. .0..0..1..0. .0..0..0..1. .0..0..0..1 %e A297506 ..1..1..0..0. .1..1..0..0. .1..1..0..0. .0..1..1..0. .0..0..1..1 %Y A297506 Column 2 is A295525. %Y A297506 Row 1 is A005251(n+2). %K A297506 nonn,tabl %O A297506 1,2 %A A297506 _R. H. Hardin_, Dec 31 2017