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 A335408 #26 Jul 21 2025 18:37:03 %S A335408 0,1,3,5,7,10,12,15,18,21 %N A335408 Diameter of nearest neighbor interchange distance for free 3-trees. %C A335408 a(n) is the maximum value of the nearest neighbor interchange distance between two unrooted binary trees with n leaves, obtained by evaluating the distance from one tree with each of the unlabeled n-leaf tree shapes (see A000672) to each labeled n-leaf tree (A001147) using the C script described in Li et al. (1996). %C A335408 The known terms a(3),...,a(12) happen (coincidentally?) to match the first ten terms of A211266. However, it seems unlikely that the sequences will agree for ever. %D A335408 Ming Li, John Tromp, and Louxin Zhang, Some notes on the nearest neighbour interchange distance, in Goos, G., Hartmanis, J., Leeuwen, J., Cai, J.-Y., and Wong, C. K., eds., "Computing and Combinatorics" 1090, Springer (Berlin, Heidelberg) (1996), 343-351. doi:10.1007/3-540-61332-3_168. %H A335408 Ming Li, John Tromp, and Louxin Zhang, <a href="https://www.researchgate.net/publication/2322259_Some_Notes_on_the_Nearest_Neighbour_Interchange_distance">Some notes on the nearest neighbour interchange distance</a>, on ResearchGate. %H A335408 Ming Li, John Tromp, and Louxin Zhang, <a href="https://doi.org/10.1006/jtbi.1996.0188">On the Nearest Neighbour Interchange Distance Between Evolutionary Trees</a>, J. Theoretical Biology, 182 (1996), 463-467. %Y A335408 Cf. A211266, which happens to have the same initial terms (offset by two). It is not clear whether this correspondence continues for higher terms. %Y A335408 A000672 gives the number of unrooted tree shapes on n leaves; A001147 gives the number of (labeled) unrooted trees. %K A335408 nonn,hard,more %O A335408 3,3 %A A335408 _Martin R. Smith_, Jun 06 2020