OFFSET
1,3
LINKS
Ron Brown and Jonathan L. Merzel, The number of Ducci sequences with given period, Fibonacci Quart. 45 (2007), no. 2, 115-121.
MATHEMATICA
a[n_] := DivisorSum[n, MoebiusMu[n/#] * 2^(#-IntegerExponent[#, 2]) &] / 2; Array[a, 35]
PROG
(PARI) a(n) = sumdiv(n, d, moebius(n/d)*2^(d-valuation(d, 2))) / 2;
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Aug 24 2023
STATUS
approved