OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..80
Marc Moskowitz, Unique connections of N circularly-spaced points, Feb 05, 2011
FORMULA
See Maple program.
MAPLE
with(numtheory);
f:=proc(n) local t0, t1, d; t0:=0;
t1:=divisors(n);
for d in t1 do
if d mod 2 = 0 then t0:=t0+phi(d)*2^(n^2/(2*d))
else t0:=t0+phi(d)*2^(n*(n-1)/(2*d)); fi;
od;
if n mod 2 = 0 then t0:=t0+n*2^(n^2/4)
else t0:=t0+n*2^((n^2-1)/4); fi;
t0/(2*n); end;
s1:=[seq(f(n), n=1..20)];
MATHEMATICA
Table[(2^((n^2-Mod[n, 2])/4) + 1/n*(Plus@@ Map[Function[d, EulerPhi[d]*2^((n*(n-Mod[d, 2])/2)/d)], Divisors[n]]))/2, {n, 1, 20}] (* From Olivier Gérard, Aug 27 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 29 2011
STATUS
approved