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 A210111 #11 Jul 13 2013 12:04:24 %S A210111 1,1,3,5,15,21,61,183,285,327,1385,4155,6681,8475,9129,50521,151563, %T A210111 247065,325947,378105,396363,2702765,8108295,13311741,17908935, %U A210111 21517869,23823015,24615741,199360981,598082943,985993845,1341471567,1643702325,1874297343 %N A210111 Left half of triangle A125053. %H A210111 Reinhard Zumkeller, <a href="/A210111/b210111.txt">Rows n=0..120 of triangle, flattened</a> %F A210111 T(n,k) = A125053(n,k), 0 <= k <= n. %o A210111 (Haskell) %o A210111 a210111 n k = a210111_tabl !! n !! k %o A210111 a210111_row n = a210111_tabl !! n %o A210111 a210111_tabl = zipWith take [1..] a125053_tabf %Y A210111 Cf. A000364 (left edge), A125054 (right edge); A210108. %K A210111 nonn,tabl %O A210111 0,3 %A A210111 _Reinhard Zumkeller_, Mar 17 2012