OFFSET
0,4
REFERENCES
Lucien Pianaro, Jouer Jeux Mathematiques, 9(juillet 1993). [From Philippe Deléham, Apr 10 2009]
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
S. Mustonen, On lines and their intersection points in a rectangular grid of points [From Seppo Mustonen, Apr 18 2009]
FORMULA
a(n) = 1/2 (f(n, 4) - 2 f(n, 3) + f(n, 2)) where f(n, k) = Sum ((n - |kx|)(n - |ky|)); -n<kx<n, -n<ky<n, (x, y)=1. [From Seppo Mustonen, Apr 18 2009]
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved