

A005500


Number of unrooted triangulations of a quadrilateral with n internal nodes.
(Formerly M1516)


20



1, 2, 5, 18, 88, 489, 3071, 20667, 146381, 1072760, 8071728, 61990477, 484182622, 3835654678, 30757242535, 249255692801, 2038827903834, 16815060576958, 139706974995635, 1168468902294726, 9831504782276593, 83174244225508659, 707159273362126228, 6039827641569969225
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OFFSET

0,2


COMMENTS

These are also called [n,1]triangulations.
Graphs can be enumerated and counted using the tool "plantri", in particular the command "./plantri s P4 c2m2 [n]".  Manfred Scheucher, Mar 08 2018


REFERENCES

C. F. Earl and L. J. March, Architectural applications of graph theory, pp. 327355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS



FORMULA



CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS

Name clarified and terms a(13) and beyond from Andrew Howroyd, Feb 22 2021


STATUS

approved



