A121121 Related to enumeration of free catapolyoctagons (see Cyvin reference for precise definition).

0, 1, 3, 26, 189, 1616, 13768, 120362, 1061728, 9465862, 85081948, 770462984, 7022416575, 64379117809, 593274806744, 5492772010760, 51068576080156, 476618665123679, 4463690012729765, 41936482657939785, 395139186154221719, 3733076854264478783

Offset

1,3

References

S. J. Cyvin, B. N. Cyvin, and J. Brunvoll. Enumeration of tree-like octagonal systems: catapolyoctagons, ACH Models in Chem. 134 (1997), 55-70.

Links

Table of n, a(n) for n=1..22.

Formula

a(n)= ( A121115(n) +A121118(n) )/4 +A036758(n/2) /2, [Cyvin eq. (50)] where sequences are zero at franctional indices. - R. J. Mathar, Jul 31 2019

Crossrefs

Sequence in context: A091262 A331862 A364634 * A355047 A228116 A091123

Adjacent sequences: A121118 A121119 A121120 * A121122 A121123 A121124

Keyword

nonn

Author

N. J. A. Sloane, Aug 13 2006

Status

approved