OFFSET
1,2
LINKS
I. Jensen, Table of n, a(n) for n = 1..55 (from link below)
I. Jensen, Series expansions for self-avoiding polygons
FORMULA
Empirical g.f.: x^2*(8 - 54*x + 214*x^2 - 489*x^3 + 605*x^4 - 386*x^5 + 177*x^6 - 120*x^7 + 19*x^8 - x^9) / (1 - 3*x + x^2)^5. - Colin Barker, Apr 17 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Aug 30 2006
STATUS
approved