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 A304068 #10 May 06 2018 08:42:10 %S A304068 0,0,1,4,14,45,140,424,1269,3760,11080,32517,95190,278154,811887, %T A304068 2367973,6903453,20120905,58639016,170894228,498084608,1451899005, %U A304068 4232957241,12343454790,36001675800,105028397290,306472665459,894497511566 %N A304068 Number of trees on n vertices rooted at an oriented non-edge. %F A304068 A000106(n) + a(n) = A000243(n). %e A304068 a(4)=4 is based on the same examples as in A304067, but the oriented edge that spans a leaf with the node at distance 2 in the linear graph may have 2 orientations, so a(4) is one larger than A304067(4). %Y A304068 Cf. A000055 (not rooted), A000106 (rooted at oriented edge) %K A304068 nonn %O A304068 1,4 %A A304068 _Brendan McKay_, May 05 2018