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A056638 Number of polygons of length 2n with two (self-avoiding polygon) holes on square lattice (not allowing rotations). 2
2, 122, 3400, 64210, 959742, 12294090, 141329502, 1500596864, 14998956452, 143004562082, 1312929589140, 11688960621918, 101451353794222, 861927965928610, 7191518458613614, 59078731187602024 (list; graph; refs; listen; history; text; internal format)
OFFSET

12,1

LINKS

I. Jensen, Table of n, a(n) for n = 12..43 (from link below)

I. Jensen, More terms

CROSSREFS

Cf. A002931.

Sequence in context: A042799 A217023 A074490 * A222873 A249497 A249498

Adjacent sequences:  A056635 A056636 A056637 * A056639 A056640 A056641

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 30 2000

STATUS

approved

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Last modified December 7 22:57 EST 2016. Contains 278899 sequences.