OFFSET
1,9
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
L. G. Sathe, On a congruence property of the divisor function, American Journal of Mathematics, Vol. 67, No. 3 (1945), pp. 397-406.
FORMULA
a(n) is asymptotic to c*n with c = 0.26....
The constant is c = 1 - zeta(3)/zeta(2) = 1 - 6*zeta(3)/Pi^2 = 0.2692370305 ... (Sathe, 1945). - Amiram Eldar, Aug 29 2020
MATHEMATICA
Accumulate[Boole[Divisible[DivisorSigma[0, Range[90]], 3]]] (* Harvey P. Dale, Jan 11 2015 *)
PROG
(PARI) a(n)=sum(k=1, n, if(numdiv(k)%3, 0, 1))
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Sep 07 2002
STATUS
approved