A292768 - OEIS

A292768

Partial sums of A065387.

2, 6, 12, 21, 31, 45, 59, 78, 97, 119, 141, 173, 199, 229, 261, 300, 334, 379, 417, 467, 511, 557, 603, 671, 722, 776, 834, 902, 960, 1040, 1102, 1181, 1249, 1319, 1391, 1494, 1568, 1646, 1726, 1832, 1914, 2022, 2108, 2212, 2314, 2408, 2502, 2642, 2741, 2854, 2958, 3080, 3186, 3324, 3436

(list; graph; refs; listen; history; text; internal format)

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