A005979 - OEIS

A005979

Number of Hamiltonian rooted triangulations with n internal nodes and 5 external nodes.
(Formerly M4000)

5, 45, 420, 4130, 42480, 453350, 4986860, 56251230, 648055650, 7601584050, 90556803600, 1093417607850, 13359234113250, 164935358510470, 2055350730457020, 25827268868350690, 326989527294142480, 4168165020885948440, 53462092704596804720, 689613220013827480620

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OFFSET

0,1

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Peter J. Taylor, Table of n, a(n) for n = 0..500

P. N. Rathie, The enumeration of Hamiltonian polygons in rooted planar triangulations, Discrete Math., 6 (1973), 163-168.

FORMULA

a(n) = f(n, 5) where f(n, k) is defined in A003122. - Sean A. Irvine, Feb 02 2015

PROG

(C#) See A003122