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 A287223 #8 May 22 2017 12:25:23 %S A287223 0,0,2,6,22,88,370,1612,7232,33304,157102,757804,3731352,18720504, %T A287223 95519428,494733144,2596388976,13783481424,73906300822,399722732236, %U A287223 2178164438936,11946745980632,65898275096796,365308080119688,2033992114316240,11369167905107888,63769939599193228,358804271821028088,2024523256299630832 %N A287223 Numbers of tree alignments. %C A287223 The notion of tree alignment is due to Jiang, Whang and Zhang (Alignment of trees—an alternative to tree edit). %D A287223 C. Chauve, J. Courtiel and Y. Ponty, Counting, Generating and Sampling Tree Alignments, in Algorithms for Computational Biology, 2016, Lecture Notes in Computer Science, vol 9702. %F A287223 G.f.: (1+sqrt(1-4*t)) * (2+8*t^2-(2-8*t) * sqrt(1-4*t)-12*t+2*sqrt(2)*R ) / (-4*t*(4*sqrt(1-4*t))) where R = sqrt((1-8*t+12*t^2)*(2*t^2+(2*t-1)*sqrt(1-4*t)+1-4*t)) (no combinatorial interpretation known). %e A287223 For n = 3, the number 6=2x3 corresponds to the number of alignments between a one-vertex tree and a two-vertices tree, or between a two-vertices tree and a one-vertex tree. %K A287223 nonn %O A287223 0,3 %A A287223 _Julien Courtiel_, May 22 2017