OFFSET
0,2
FORMULA
See A065775.
Empirical g.f.: -4*x*(2*x^8+2*x^7-4*x^6-5*x^5-2*x^4-x^3-5*x^2-8*x-5) / ((x-1)^4*(x+1)^2*(x^2+x+1)). - Colin Barker, May 04 2014
EXAMPLE
a(2)=52 counts the knight's moves to these points:
4 1 2 1 4
1 2 3 2 1
2 3 0 3 2
1 2 3 2 1
4 1 2 1 4
a(0)=0 for the center, and a(1)=20 for the square
2 3 2
3 0 3
2 3 2
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Dec 20 2010
STATUS
approved