OFFSET
1,1
LINKS
N. J. A. Sloane, Table of n, a(n) for n = 1..10000
FORMULA
G.f.: (1/(1 - x))*Sum_{k>=1} (mu(k) + 1)*x^k/(1 - x^k)^2. - Ilya Gutkovskiy, Sep 28 2017
a(n) = (3/(Pi^2) + Pi^2/12) * n^2 + O(n*log(n)). - Amiram Eldar, Dec 03 2023
MATHEMATICA
Accumulate @ Table[EulerPhi[n] + DivisorSigma[1, n], {n, 100}] (* Amiram Eldar, Dec 03 2023 *)
PROG
(PARI) lista(nmax) = {my(f, s = 0); for(n = 1, nmax, f = factor(n); s += (sigma(f) + eulerphi(f)); print1(s, ", ")); } \\ Amiram Eldar, Dec 03 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 28 2017
STATUS
approved