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 A190097 #7 Jul 22 2025 12:01:53 %S A190097 8,39,100,204,344,527,736,984,1244,1520,1796,2104,2412,2736,3076,3438, %T A190097 3800,4184,4568,4968,5376,5800,6224,6668,7120,7588,8056,8540,9024, %U A190097 9524,10024,10542,11060,11594,12136,12694,13252,13826,14400,14990,15580,16186 %N A190097 Number of rhombuses on a (n+1)X9 grid. %C A190097 Column 8 of A190098 %H A190097 R. H. Hardin, <a href="/A190097/b190097.txt">Table of n, a(n) for n = 1..200</a> %F A190097 Empirical: a(n) = 2*a(n-1) -2*a(n-3) +a(n-4) for n>51 %e A190097 Some solutions for n=3 %e A190097 ..0..3....1..1....1..5....0..5....0..5....1..0....0..5....0..4....2..4....1..3 %e A190097 ..0..5....1..2....2..2....0..7....1..7....1..1....1..4....1..2....2..5....1..5 %e A190097 ..2..5....2..2....3..5....2..7....3..6....2..1....2..5....2..4....3..5....3..5 %e A190097 ..2..3....2..1....2..8....2..5....2..4....2..0....1..6....1..6....3..4....3..3 %K A190097 nonn %O A190097 1,1 %A A190097 _R. H. Hardin_ May 04 2011