A332651 Number of polygonal cacti on n unlabeled nodes with every polygon having an even number of edges.

1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 4, 2, 7, 9, 14, 26, 48, 71, 154, 243, 478, 894, 1631, 3149, 6062, 11295, 22469, 42900, 83528, 164829, 321012, 632960, 1255613, 2472803, 4928140, 9808439, 19533534, 39134059, 78345317, 157177556, 316398963, 636790282, 1284910954

Offset

0,11

Comments

Bridges are disallowed.

Links

Andrew Howroyd, Table of n, a(n) for n = 0..200

Wikipedia, Cactus graph

Index entries for sequences related to cacti

Example

a(6) = 1 corresponding with a hexagon.
a(7) = 1 corresponding with two quadrilaterals joined at a node.

Prog

(PARI) \\ See A332650 for UCacti.
seq(n)={concat([1], UCacti(vector(n, i, i>2&&i%2==0)))}

Crossrefs

Cf. A000083, A035085, A091487, A332649, A332650.

Sequence in context: A203575 A120871 A019689 * A072009 A257502 A201207

Adjacent sequences: A332648 A332649 A332650 * A332652 A332653 A332654

Keyword

nonn

Author

Andrew Howroyd, Feb 18 2020

Status

approved