OFFSET
1,3
REFERENCES
József Sándor, Dragoslav S. Mitrinovic, Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, Chapter V, page 164.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
E. Heppner, Über die Iteration von Teilerfunktionen, Journal für die reine und angewandte Mathematik, Vol. 265 (1974), pp. 176-182.
G. J. Rieger, Über einige arithmetische Summen, Manuscripta Mathematica, Vol. 7 (1972), pp. 23-34.
FORMULA
a(n) = n*log(log(n)) + O(n).
a(n) = b * n * log(log(n)) + Sum_{k=0..floor(sqrt(n))} b_k * n/log(n)^k + O(n * exp(-c*sqrt(log(n)))), where b, b_k and c are constants (Heppner, 1974). b = 1 and b_0 = B + C, where B is Mertens's constant (A077761), C = Sum_{k>=2} A076191(k)*P(k) = 0.12861146810484151346..., and P(s) is the prime zeta function. - Amiram Eldar, Jan 15 2024 and Feb 11 2024
MATHEMATICA
Accumulate[PrimeOmega[DivisorSigma[0, Range[70]]]] (* Harvey P. Dale, Dec 05 2013 *)
PROG
(PARI) a(n)=sum(i=1, n, bigomega(numdiv(i)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Benoit Cloitre, Feb 02 2003
STATUS
approved