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A007816 Number of abstract simplicial 2-complexes on {1,2,3,...,n+3} which triangulate the 2-sphere: C(n+3,2)*(4n+1)!/(3n+3)!. 3
1, 10, 195, 5712, 223440, 10929600, 641277000, 43859692800, 3424685806080, 300495408595200, 29262949937020800, 3131187613956864000, 365112996737448960000, 46075561988281233408000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Foulds, L. R. Enumeration of graph theoretic solutions for facilities layout. Proceedings of the sixteenth Southeastern international conference on combinatorics, graph theory and computing (Boca Raton, Fla., 1985). Congr. Numer. 48 (1985), 87--99. MR0830702(87f:90045). See Table 2. - From N. J. A. Sloane, Apr 06 2012

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

William T. Tutte, A census of planar triangulations, Canad. J. Math. 14 (1962), 21-38.

MAPLE

A007816:=n->binomial(n+3, 2)*(4*n+1)!/(3*n+3)!; seq(A007816(n), n=1..20);

MATHEMATICA

Table[Binomial[n+3, 2] (4n+1)!/(3n+3)!, {n, 20}] (* Harvey P. Dale, May 16 2012 *)

PROG

(MAGMA) [Binomial(n+3, 2)*Factorial(4*n+1)/Factorial(3*n+3): n in [1..20]]; // Vincenzo Librandi, May 21 2012

CROSSREFS

Sequence in context: A006436 A252974 A187652 * A126463 A239766 A294047

Adjacent sequences:  A007813 A007814 A007815 * A007817 A007818 A007819

KEYWORD

nonn,easy,nice

AUTHOR

Victor Reiner (reiner(AT)math.umn.edu), Paul Edelman (edelman(AT)math.umn.edu)

STATUS

approved

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Last modified October 23 13:11 EDT 2018. Contains 316528 sequences. (Running on oeis4.)