A129114 Number of unrooted unlabeled connected triangular maps on a compact closed oriented surface with 2n faces (and thus 3n edges).

1, 3, 11, 81, 1228, 28174, 843186, 30551755, 1291861997, 62352938720, 3381736322813, 203604398647922, 13475238697911184, 972429507963453210, 75993857157285258473, 6393779463050776636807, 576237114190853665462712, 55385308766655472416299110, 5655262782600929403228668176

Offset

0,2

Comments

Equivalently, the number of pairs of permutations (sigma,tau) up to simultaneous conjugacy on a set of size 6*n with sigma^3=tau^2=1, acting transitively and with no fixed point.

Links

Andrew Howroyd, Table of n, a(n) for n = 0..300

Formula

Inverse Euler transform of A129115. - Andrew Howroyd, Jan 29 2025

Crossrefs

Column 3 of A380626.

Connected version of A129115.

Unrooted version of A062980.

Cf. also A121350, A121352, A005133.

Sequence in context: A163856 A232468 A099341 * A136649 A342058 A062580

Adjacent sequences: A129111 A129112 A129113 * A129115 A129116 A129117

Keyword

nonn,changed

Author

Samuel A. Vidal, Mar 30 2007

Extensions

a(0)=1 prepended and terms a(17) onwards from Andrew Howroyd, Jan 29 2025

Status

approved