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A091468 Number of unlabeled alternating octupi with n black nodes and n white nodes. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 30 22:55 EDT 2020. Contains 333132 sequences. (Running on oeis4.)