A094155 Bisection of A000939.

2, 14, 332, 18264, 1664354, 222406776, 40865005494, 9880209206458, 3041127561315224, 1161157777643184900, 538583682082245127336, 298292500833816420226008, 194444097328912809590995986, 147362699895662080130636012160, 128481853971530055408959624233748, 127695847335468919414701788927638656

Offset

2,1

Links

Table of n, a(n) for n=2..17.

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

Adjacent sequences: A094152 A094153 A094154 * A094156 A094157 A094158

Keyword

nonn

Author

N. J. A. Sloane, May 05 2004

Status

approved