

A332651


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


3



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
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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



