A094155 - OEIS

%I #6 Oct 01 2017 03:02:02

%S 2,14,332,18264,1664354,222406776,40865005494,9880209206458,

%T 3041127561315224,1161157777643184900,538583682082245127336,

%U 298292500833816420226008,194444097328912809590995986,147362699895662080130636012160,128481853971530055408959624233748,127695847335468919414701788927638656

%N Bisection of A000939.

%H S. W. Golomb and L. R. Welch, <a href="http://www.jstor.org/stable/2308978">On the enumeration of polygons</a>, Amer. Math. Monthly, 67 (1960), 349-353.

%F See Maple line.

%p 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;

%K nonn

%O 2,1

%A _N. J. A. Sloane_, May 05 2004