OFFSET
1,2
COMMENTS
a(n) = denominator of Sum_{d|n} 1 / A000005(d).
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..5000
FORMULA
EXAMPLE
For n = 6; divisors d of 6: {1, 2, 3, 6}; tau(d): {1, 2, 2, 4}; Sum_{d|6} 1 / tau(d) = 1/1 + 1/2 + 1/2 + 1/4 = 9 / 4; a(n) = 4 (denominator).
MATHEMATICA
Table[Denominator[Sum[1/DivisorSigma[0, d], {d, Divisors@ n}]], {n, 83}] (* Michael De Vlieger, Dec 09 2015 *)
PROG
(Magma) [Denominator(&+[1/NumberOfDivisors(d): d in Divisors(n)]): n in [1..1000]]
(PARI) a(n) = denominator(sumdiv(n, d, 1/numdiv(d))); \\ Michel Marcus, Dec 09 2015
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Jaroslav Krizek, Dec 08 2015
STATUS
approved