Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #12 Dec 03 2023 05:01:33
%S 2,6,12,21,31,45,59,78,97,119,141,173,199,229,261,300,334,379,417,467,
%T 511,557,603,671,722,776,834,902,960,1040,1102,1181,1249,1319,1391,
%U 1494,1568,1646,1726,1832,1914,2022,2108,2212,2314,2408,2502,2642,2741,2854,2958,3080,3186,3324,3436
%N Partial sums of A065387.
%H N. J. A. Sloane, <a href="/A292768/b292768.txt">Table of n, a(n) for n = 1..10000</a>
%F G.f.: (1/(1 - x))*Sum_{k>=1} (mu(k) + 1)*x^k/(1 - x^k)^2. - _Ilya Gutkovskiy_, Sep 28 2017
%F a(n) = (3/(Pi^2) + Pi^2/12) * n^2 + O(n*log(n)). - _Amiram Eldar_, Dec 03 2023
%t Accumulate @ Table[EulerPhi[n] + DivisorSigma[1, n], {n, 100}] (* _Amiram Eldar_, Dec 03 2023 *)
%o (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
%Y Cf. A000010, A000203, A065387.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Sep 28 2017