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 A273968 #4 Jun 05 2016 14:38:49 %S A273968 1,2,2,5,10,5,15,105,105,15,51,1264,1946,1264,51,187,13045,24587, %T A273968 24587,13045,187,715,136063,211121,49534,211121,136063,715,2795, %U A273968 1273961,2116450,36817,36817,2116450,1273961,2795,11051,11936399,15084593,40569 %N A273968 T(n,k)=Number of nXk 0..3 arrays with no three equal values forming an isosceles triangle, and new values introduced in 0..3 order. %C A273968 Table starts %C A273968 ......1..........2..........5....15.....51.....187......715......2795.....11051 %C A273968 ......2.........10........105..1264..13045..136063..1273961..11936399..95697853 %C A273968 ......5........105.......1946.24587.211121.2116450.15084593.112714143.511843593 %C A273968 .....15.......1264......24587.49534..36817...40569....36570.....90627.....89429 %C A273968 .....51......13045.....211121.36817....356......10........0.........0 %C A273968 ....187.....136063....2116450.40569.....10.......0........0 %C A273968 ....715....1273961...15084593.36570......0.......0 %C A273968 ...2795...11936399..112714143.90627......0 %C A273968 ..11051...95697853..511843593.89429 %C A273968 ..43947..800561388.2841058530 %C A273968 .175275.5824237329 %C A273968 .700075 %H A273968 R. H. Hardin, <a href="/A273968/b273968.txt">Table of n, a(n) for n = 1..82</a> %F A273968 Empirical for column k: %F A273968 k=1: a(n) = 7*a(n-1) -14*a(n-2) +8*a(n-3) %e A273968 Some solutions for n=4 k=4 %e A273968 ..0..0..1..2. .0..1..2..1. .0..1..0..2. .0..0..1..0. .0..0..1..1 %e A273968 ..3..1..0..0. .0..3..2..3. .3..3..3..2. .2..3..3..3. .2..1..2..0 %e A273968 ..3..1..3..3. .0..3..2..3. .1..2..2..1. .3..2..1..1. .3..1..3..0 %e A273968 ..0..2..1..2. .2..1..0..0. .0..1..0..1. .1..0..2..2. .3..1..3..2 %Y A273968 Column 1 is A007581(n-1). %K A273968 nonn,tabl %O A273968 1,2 %A A273968 _R. H. Hardin_, Jun 05 2016