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

Offset: 1

Author

N. J. A. Sloane, Sep 28 2017

Keywords

• nonn

Links

• N. J. A. Sloane, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A000203, A065387.

Programs

Mathematica

Accumulate @ Table[EulerPhi[n] + DivisorSigma[1, n], {n, 100}] (* Amiram Eldar, Dec 03 2023 *)

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

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