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 A197250 #7 Jun 02 2025 04:48:59 %S A197250 1,2,2,1,4,1,1,8,8,1,3,16,3,16,3,3,40,53,53,40,3,2,80,110,275,110,80, %T A197250 2,4,192,227,780,780,227,192,4,6,400,1035,5713,5062,5713,1035,400,6,5, %U A197250 936,2004,16773,31276,31276,16773,2004,936,5,6,1984,7529,98870,213912,405065 %N A197250 T(n,k)=Number of nXk 0..4 arrays with each element x equal to the number of its horizontal and vertical neighbors equal to 0,0,1,1,1 for x=0,1,2,3,4. %C A197250 Every 0 is next to 0 0's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 1's, every 4 is next to 4 1's %C A197250 Table starts %C A197250 .1....2.....1.......1........3..........3............2.............4 %C A197250 .2....4.....8......16.......40.........80..........192...........400 %C A197250 .1....8.....3......53......110........227.........1035..........2004 %C A197250 .1...16....53.....275......780.......5713........16773.........98870 %C A197250 .3...40...110.....780.....5062......31276.......213912.......1244680 %C A197250 .3...80...227....5713....31276.....405065......3264225......29975706 %C A197250 .2..192..1035...16773...213912....3264225.....48703999.....692974749 %C A197250 .4..400..2004...98870..1244680...29975706....692974749...11304892092 %C A197250 .6..936..7529..393913..8149652..324191969...9613268927..308547360234 %C A197250 .5.1984.20633.1869033.54813300.2687575073.144634486646.5580867056186 %H A197250 R. H. Hardin, <a href="/A197250/b197250.txt">Table of n, a(n) for n = 1..199</a> %e A197250 Some solutions containing all values 0 to 4 for n=6 k=4 %e A197250 ..0..1..1..2....1..2..2..1....1..0..1..1....0..1..1..0....1..0..1..1 %e A197250 ..1..1..0..1....0..1..1..0....1..1..2..0....2..1..4..1....2..1..3..0 %e A197250 ..1..3..2..1....2..1..4..1....0..1..3..1....1..0..1..2....0..1..1..2 %e A197250 ..0..1..1..0....1..0..1..1....1..4..1..3....1..3..1..0....1..1..0..1 %e A197250 ..1..1..4..1....2..1..1..0....1..1..0..1....0..1..1..2....1..4..1..2 %e A197250 ..1..0..1..2....0..1..3..1....0..1..1..2....1..1..0..1....0..1..1..0 %Y A197250 Column 1 is A017817(n+5) %K A197250 nonn,tabl %O A197250 1,2 %A A197250 _R. H. Hardin_ Oct 12 2011