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 A246566 #7 Aug 31 2014 02:00:36 %S A246566 1,1,2,4,10,24,62,155,396,992,2504,6228,15512,38220,94059,229498, %T A246566 558642,1350384,3255138,7801327,18642118,44329833,105111283,248184255, %U A246566 584396849,1371048495,3208318247,7483522231,17413665881,40405120865,93543352492 %N A246566 Number of rooted ordered trees with n non-root nodes such that the branch lengths are weakly decreasing. %H A246566 Joerg Arndt, <a href="/A246566/a246566.txt">All trees for 0 <= n <= 5</a> %e A246566 The a(3) = 4 such trees are: %e A246566 : %e A246566 : 1: %e A246566 : [ 1 1 1 ] %e A246566 : [ 0 0 0 ] %e A246566 : %e A246566 : O--o %e A246566 : .--o %e A246566 : .--o %e A246566 : %e A246566 : %e A246566 : 2: %e A246566 : [ 2 1 ] %e A246566 : [ 0 0 ] %e A246566 : %e A246566 : O--o--o %e A246566 : .--o %e A246566 : %e A246566 : %e A246566 : 3: %e A246566 : [ 2 1 ] %e A246566 : [ 0 1 ] %e A246566 : %e A246566 : O--o--o %e A246566 : .--o %e A246566 : %e A246566 : %e A246566 : 4: %e A246566 : [ 3 ] %e A246566 : [ 0 ] %e A246566 : %e A246566 : O--o--o--o %e A246566 : %e A246566 See the Arndt link for all trees for 0 <= n <= 5. %Y A246566 Cf. A000108 (all trees), A246565 (ascending branch lengths), A193196, A192243, A001519. %K A246566 nonn %O A246566 0,3 %A A246566 _Joerg Arndt_, Aug 30 2014