A091468 Number of unlabeled alternating octupi with n black nodes and n white nodes.

1, 4, 10, 28, 76, 238, 736, 2428, 8110, 27754, 96196, 338158, 1200070, 4298578, 15511810, 56352508, 205906432, 756265486, 2790415564, 10338503578, 38446991530, 143461341082, 536962873540, 2015475400942, 7584636386326

Offset

1,2

Links

Table of n, a(n) for n=1..25.

Formula

3*A003239(n) - 2 (conjectured). - Ralf Stephan, Feb 06 2004

Crossrefs

Main diagonal of A091467.

Sequence in context: A121302 A026150 A026123 * A103457 A083587 A228403

Adjacent sequences: A091465 A091466 A091467 * A091469 A091470 A091471

Keyword

nonn

Author

Christian G. Bower, Jan 12 2004

Status

approved