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A094155
Bisection of A000939.
3
2, 14, 332, 18264, 1664354, 222406776, 40865005494, 9880209206458, 3041127561315224, 1161157777643184900, 538583682082245127336, 298292500833816420226008, 194444097328912809590995986, 147362699895662080130636012160, 128481853971530055408959624233748, 127695847335468919414701788927638656
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
Sequence in context: A165696 A180605 A358597 * A132626 A101524 A346210
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 05 2004
STATUS
approved