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 A304067 #13 May 06 2018 08:36:59 %S A304067 0,0,1,3,9,27,79,233,679,1987,5784,16864,49063,142821,415439,1208761, %T A304067 3516475,10232428,29778138,86682119,252382445,735040515,2141319946, %U A304067 6239913801,18188637903,53033228465,154674931182,451247206423 %N A304067 Number of trees with n vertices rooted at a non-edge. %F A304067 a(n) + A027852(n) = A303833(n). %e A304067 a(3)=1: the non-edge joins two leaves. a(4)=3: The non-edge joins two leaves of the star graph; or the non-edge joins the two leaves of the linear graph; or the non-edge joins a leaf with the node at distance 2. %Y A304067 Cf. A000055 (not rooted), A027852 (rooted at an edge), A304068 (rooted at an oriented non-edge). %K A304067 nonn %O A304067 1,4 %A A304067 _Brendan McKay_, May 05 2018