OFFSET
2,1
LINKS
S. W. Golomb and L. R. Welch, On the enumeration of polygons, Amer. Math. Monthly, 67 (1960), 349-353.
FORMULA
See Maple line.
MAPLE
with(numtheory); f:=proc(n) local t1, d; t1:=2^(n/2)*(n/2)*(n/2)!; for d from 1 to n do if n mod d = 0 then t1:=t1+phi(n/d)^2*d!*(n/d)^d; fi; od: t1/(2*n^2); end;
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 05 2004
STATUS
approved