This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A369779 #18 Jul 10 2025 14:17:48
%S A369779 0,1,1,2,1,8,1,8,6,22,1,20,1,44,26,32,1,66,1,48,48,112,1,80,20,158,54,
%T A369779 92,1,172,1,128,116,274,62,156,1,344,162,192,1,348,1,228,174,508,1,
%U A369779 320,42,540,278,320,1,594,130,368,348,814,1,448,1,932,306,512,176
%N A369779 a(n) = n * Sum_{p|n, p prime} phi(n/p) / p.
%C A369779 Dirichlet convolution of A010051(n) and A002618(n). - _Wesley Ivan Hurt_, Jul 10 2025
%H A369779 Antti Karttunen, <a href="/A369779/b369779.txt">Table of n, a(n) for n = 1..20000</a>
%F A369779 From _Wesley Ivan Hurt_, Jul 10 2025: (Start)
%F A369779 a(n) = Sum_{d|n} A010051(d) * A002618(n/d).
%F A369779 a(p^k) = ceiling(p^(2k-2)-p^(2k-3)) for p prime and k>=1. (End)
%t A369779 Table[n*DivisorSum[n, EulerPhi[n/#]/# &, PrimeQ[#] &], {n, 100}]
%o A369779 (PARI) A369779(n) = if(1==n, 0, my(f=factor(n)); n*sum(i=1, #f~, (eulerphi(n/f[i, 1])/f[i,1]))); \\ _Antti Karttunen_, Jan 23 2025
%Y A369779 Cf. A000010, A002618, A010051, A057660, A117494, A347104, A369687.
%Y A369779 Cf. also A369894, A369907, A369909.
%K A369779 nonn,easy
%O A369779 1,4
%A A369779 _Wesley Ivan Hurt_, Jan 31 2024