OFFSET
0,2
LINKS
A. J. Guttmann and A. R. Conway, Self-Avoiding Walks and Polygons, Annals of Combinatorics 5 (2001) 319-345.
FORMULA
a(n) = 4*A336662(n).
EXAMPLE
a(5) = 40. The five possible 5-step walks in the first quadrant are:
.
+--+ +--+ +--+ +--+
| | | |
+--+ +--+ +--+ +--+ +--+
| | | | | |
x--+ x--+ x--+ x--+ x--+ +--+
.
Each of these can be taken in eight ways on the square lattice, giving 40 in total.
CROSSREFS
KEYWORD
nonn,walk
AUTHOR
Scott R. Shannon, Aug 24 2020
STATUS
approved