A325455 Triangle read by rows: T(n,k) is the number of simple connected graphs on n unlabeled nodes with circumference k, (n >= 3, k >= 3).

1, 1, 3, 4, 6, 8, 10, 24, 24, 48, 30, 87, 116, 226, 383, 83, 342, 527, 1283, 2663, 6196, 257, 1324, 2644, 6644, 17613, 55468, 177083

Offset

3,3

Comments

Trees are excluded since they do not have any cycle.

Links

Table of n, a(n) for n=3..30.

Eric Weisstein's World of Mathematics, Graph Circumference

Eric Weisstein's World of Mathematics, Hamiltonian Graph

Example

Triangle begins:
    1;
    1,    3;
    4,    6,    8;
   10,   24,   24,   48;
   30,   87,  116,  226,   383;
   83,  342,  527, 1283,  2663,  6196;
  257, 1324, 2644, 6644, 17613, 55468, 177083;
  ...

Crossrefs

Right diagonal is A003216.

Row sums are A241841.

Cf. A128042, A309524, A325447.

Sequence in context: A343883 A277319 A176986 * A337455 A080728 A047414

Adjacent sequences: A325452 A325453 A325454 * A325456 A325457 A325458

Keyword

nonn,tabl,more,changed

Author

Andrew Howroyd, Sep 06 2019

Status

approved