A005508 Number of unrooted triangulations with reflection symmetry of a disk with one internal node and n+3 nodes on the boundary. (Formerly M0755)

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

0,2

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.

Sequence in context: A103065 A281142 A110448 * A022542 A220418 A064450

Adjacent sequences: A005505 A005506 A005507 * A005509 A005510 A005511

Keyword

nonn

Author

N. J. A. Sloane

Extensions

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

Status

approved