OFFSET
1,3
COMMENTS
First occurrence of k > 0: 1, 10, 14, 21, 22, 26, 116, 15, 38, 164, 46, 57, 212, 58, 62, 390, 1096, 74, 45840, 33, ...;
First occurrence of k < 0: 2, 3, 228, 5, 132, 7, 516, 204, 728, 11, 276, 13, 948, 258, 308, 17, 1236, 19, 5496, 366, ..., .
LINKS
Mats Granvik and Robert G. Wilson v, Table of n, a(n) for n = 1..10000
EXAMPLE
a(6) = 1 since mu(6)/1 + mu(3)/2 + mu(2)/3 + mu(1)/6 = 1 - 1/2 - 1/3 + 1/6 = 1/3.
MAPLE
f:= n -> numer(add(numtheory:-mobius(n/k)/k, k=numtheory:-divisors(n))):
map(f, [$1..100]); # Robert Israel, Nov 16 2017
MATHEMATICA
f[n_] := Block[{d = Divisors@ n}, Plus @@ (MoebiusMu[d]/Reverse@ d)]; Numerator@ Array[f, 70]
PROG
(PARI) a(n) = numerator(sumdiv(n, d, moebius(n/d)/d)); \\ Michel Marcus, Nov 17 2017
CROSSREFS
KEYWORD
sign,look
AUTHOR
Mats Granvik and Robert G. Wilson v, Nov 15 2017
STATUS
approved