A303839 Number of noncrossing path sets on n nodes up to rotation and reflection with each path having at least two nodes.

1, 0, 1, 1, 3, 5, 17, 40, 138, 430, 1546, 5478, 20525, 77310, 298301, 1161692, 4583525, 18239037, 73221198, 296046399, 1205038270, 4933969005, 20311807087, 84029440358, 349201537324, 1457205298510, 6104204225832, 25661191956781, 108231773165825

Offset

0,5

Links

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

Example

Case n=4: There are 3 possibilities:
.
   o---o   o   o   o---o
           |   |     /
   o---o   o---o   o---o
.

Prog

(PARI) \\ See A303731 for NCPathSetsModDihedral
Vec(NCPathSetsModDihedral(vector(30, k, k>1)))

Crossrefs

Cf. A303730, A303731, A303835, A303844.

Sequence in context: A148519 A148520 A148521 * A148522 A308588 A141160

Adjacent sequences: A303836 A303837 A303838 * A303840 A303841 A303842

Keyword

nonn

Author

Andrew Howroyd, May 01 2018

Status

approved