OFFSET
0,4
COMMENTS
a(n) = total length of all cycles (see A000048) which are strictly less than the full length of 2n.
REFERENCES
R. K. Guy, Posting to Sequence Fans Mailing List, Apr 20 2012
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..2000
MAPLE
with (numtheory):
a:= n-> 2^n -add (mobius(d)*2^(n/d), d=select(x->is(x, odd), divisors(n))):
seq (a(n), n=0..80); # Alois P. Heinz, Apr 21 2012
MATHEMATICA
a[n_] := 2^n - DivisorSum[n, Mod[#, 2]*MoebiusMu[#]*2^(n/#)&]; a[0] = 1;
Table[a[n], {n, 0, 80}] (* Jean-François Alcover, Mar 27 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 21 2012
STATUS
approved