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 A131427 #17 May 20 2016 18:44:05 %S A131427 1,0,1,0,0,2,0,0,0,5,0,0,0,0,14,0,0,0,0,0,42,0,0,0,0,0,0,132,0,0,0,0, %T A131427 0,0,0,429,0,0,0,0,0,0,0,0,1430,0,0,0,0,0,0,0,0,0,4862,0,0,0,0,0,0,0, %U A131427 0,0,0,16796,0,0,0,0,0,0,0,0,0,0,0,58786,0,0,0,0,0,0,0,0,0,0,0,0,208012 %N A131427 A000108(n) preceded by n zeros. %C A131427 Triangle given by A000004 DELTA A000012 where DELTA is the operator defined in A084938. - _Philippe Deléham_, Jul 12 2007 %C A131427 T(n,k) is the number of Dyck paths of semilength n having exactly k U=(1,1) steps. - _Alois P. Heinz_, Jun 09 2014 %H A131427 Alois P. Heinz, <a href="/A131427/b131427.txt">Rows n = 0..140, flattened</a> %F A131427 A000108(n) preceded by n zeros, as an infinite lower triangular matrix. %e A131427 First few rows of the triangle are: %e A131427 1; %e A131427 0, 1; %e A131427 0, 0, 2; %e A131427 0, 0, 0, 5; %e A131427 0, 0, 0, 0, 14; %e A131427 0, 0, 0, 0, 0, 42; %e A131427 ... %p A131427 T:= (n, k)-> `if`(k<n, 0, binomial(2*n, n)/(n+1)): %p A131427 seq(seq(T(n, k), k=0..n), n=0..15); # _Alois P. Heinz_, Jun 09 2014 %t A131427 T[n_, n_] := CatalanNumber[n]; T[_, _] = 0; %t A131427 Table[T[n, k], {n, 0, 15}, {k, 0, n}] // Flatten (* _Jean-François Alcover_, May 20 2016 *) %Y A131427 Cf. A131428, A131429, A000108, A243752. %K A131427 nonn,tabl %O A131427 0,6 %A A131427 _Gary W. Adamson_, Jul 10 2007 %E A131427 More terms from _Philippe Deléham_, Oct 16 2008