A048781 Number of triangles in minimal triangle graphs.

1, 2, 5, 13, 35, 86, 250, 687, 2001, 5897, 17847, 54683, 170578, 537468, 1714312, 5516392, 17910741, 58588966, 193035920, 640132185, 2135841554, 7167550473, 24186506740

Offset

3,2

Comments

a(n) is the total number of triples in all the minimal triangle graphs on n points. That is, a(n) = Sum |T| for all A000080(n) triangle graphs G(T) on n points.

Links

Table of n, a(n) for n=3..25.

R. Bowen, The generation of minimal triangle graphs, Math. Comp. 21 (1967), 248-250.

Example

For n=3 points there is one minimal triangle graph containing one triple, so a(3) = 1.
For n=4 points there is one triangle graph containing two triples, so a(4) = 2.
For n=5 points there are two graphs, containing two and three triples, respectively, so a(5) = 2+3 = 5.
See also the illustration in A000080.

Crossrefs

Cf. A000080.

Sequence in context: A112839 A331755 A137674 * A291242 A097919 A160438

Adjacent sequences: A048778 A048779 A048780 * A048782 A048783 A048784

Keyword

nonn,more,nice

Author

Arlin Anderson (starship1(AT)gmail.com)

Extensions

Edited by N. J. A. Sloane, Jan 22 2014

a(17)-a(25) from Martin Fuller, Mar 23 2015

Status

approved