cp's OEIS Frontend

A005502 Number of unrooted triangulations of a hexagon with n internal nodes.

%I A005502 M2904 #35 Feb 23 2021 10:06:16
%S A005502 3,11,53,295,1867,12560,89038,652198,4903955,37627699,293607612,
%T A005502 2323604832,18614121391,150704813812,1231596828200,10148762396401,
%U A005502 84252059397251,704122279126074,5920239345451780,50051285956517452,425273487358680290,3630084126997807369
%N A005502 Number of unrooted triangulations of a hexagon with n internal nodes.
%C A005502 These are also called [n,3]-triangulations.
%C A005502 Graphs can be enumerated and counted using the tool "plantri", in particular the command "./plantri -s -P6 -c2m2 [n]". - _Manfred Scheucher_, Mar 08 2018
%D A005502 C. F. Earl and L. J. March, Architectural applications of graph theory, pp. 327-355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979.
%D A005502 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A005502 Andrew Howroyd, <a href="/A005502/b005502.txt">Table of n, a(n) for n = 0..200</a>
%H A005502 G. Brinkmann and B. McKay, <a href="http://users.cecs.anu.edu.au/~bdm/plantri/">Plantri (program for generation of certain types of planar graph)</a>
%H A005502 C. F. Earl and L. J. March, <a href="/A005500/a005500_1.pdf">Architectural applications of graph theory</a>, pp. 327-355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979. (Annotated scanned copy)
%H A005502 C. F. Earl & N. J. A. Sloane, <a href="/A005500/a005500.pdf">Correspondence, 1980-1981</a>
%F A005502 a(n) = (A005507(n) + A005495(n))/2 (based on Max Alekseyev's formula, cf. A005501 and A005500).
%Y A005502 Column k=3 of the array in A169808.
%Y A005502 Cf. A005507, A005495.
%K A005502 nonn
%O A005502 0,1
%A A005502 _N. J. A. Sloane_
%E A005502 a(5)-a(10) from _Manfred Scheucher_, Mar 08 2018
%E A005502 Name clarified and terms a(11) and beyond from _Andrew Howroyd_, Feb 22 2021