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A007221 Almost-convex polygons of perimeter 2n on square lattice.
(Formerly M4304)
0
6, 216, 3706, 44060, 417486, 3386912, 24554562, 163587572, 1020918342, 6050527496, 34395992698, 188971062108, 1009130882494, 5261414979024 (list; graph; refs; listen; history; text; internal format)
OFFSET

8,1

REFERENCES

I. G. Enting, A. J. Guttmann, L. B. Richmond and N. C. Wormald, Enumeration of almost-convex polygons on the square lattice, Random Structures Algorithms 3 (1992), 445-461.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=8..21.

CROSSREFS

Sequence in context: A002037 A030265 A275567 * A195802 A145249 A154023

Adjacent sequences:  A007218 A007219 A007220 * A007222 A007223 A007224

KEYWORD

nonn

AUTHOR

Simon Plouffe

STATUS

approved

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Last modified July 17 20:45 EDT 2019. Contains 325109 sequences. (Running on oeis4.)