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 A240617 #7 Apr 10 2014 11:52:48
%S A240617 1,1,2,5,14,46,165,651,2771,12638,61398,315563,1710027,9725543,
%T A240617 57886132,359476571,2323518017,15597303757,108522502933,781283103284,
%U A240617 5810573402452,44579551962460,352360829928066,2865876353091752,23958937424819348,205673285003637629
%N A240617 Number of n-length words w over an n-ary alphabet such that w is empty or a prefix z concatenated with letter a_i and i=1 or 0 < #(z,a_{i-1}) >= #(z,a_i), where #(z,a_i) counts the occurrences of the i-th letter in z.
%e A240617 a(0) = 1: the empty word.
%e A240617 a(1) = 1: 1.
%e A240617 a(2) = 2: 11, 12.
%e A240617 a(3) = 5: 111, 112, 121, 122, 123.
%e A240617 a(4) = 14: 1111, 1112, 1121, 1122, 1123, 1211, 1212, 1213, 1221, 1223, 1231, 1232, 1233, 1234.
%e A240617 a(5) = 46: 11111, 11112, 11121, ..., 12343, 12344, 12345.
%e A240617 a(6) = 165: 111111, 111112, 111121, ..., 123454, 123455, 123456.
%Y A240617 Main diagonal of A240608.
%K A240617 nonn
%O A240617 0,3
%A A240617 _Alois P. Heinz_, Apr 09 2014