A005508 Number of unrooted triangulations with reflection symmetry of a disk with one internal node and n+3 nodes on the boundary.

1, 2, 3, 6, 8, 18, 23, 56, 70, 180, 222, 594, 726, 2002, 2431, 6864, 8294, 23868, 28730, 83980, 100776, 298452, 357238, 1069776, 1277788, 3863080, 4605980, 14040810, 16715250, 51325650, 61020495, 188574240, 223931910, 695987820, 825632610, 2579248980

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

Comments

These are also called [1,n]-triangulations.

References

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

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..1000
• 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. (Annotated scanned copy)
• C. F. Earl & N. J. A. Sloane, Correspondence, 1980-1981

Crossrefs

Row n=1 of the array in A169809.

Extensions

Name clarified and terms a(7) and beyond from Andrew Howroyd, Feb 22 2021