A369779 - OEIS

%I #13 Jan 23 2025 17:42:43

%S 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 92,1,172,1,128,116,274,62,156,1,344,162,192,1,348,1,228,174,508,1,

%U 320,42,540,278,320,1,594,130,368,348,814,1,448,1,932,306,512,176

%N a(n) = n * Sum_{p|n, p prime} phi(n/p) / p.

%H Antti Karttunen, <a href="/A369779/b369779.txt">Table of n, a(n) for n = 1..20000</a>

%t Table[n*DivisorSum[n, EulerPhi[n/#]/# &, PrimeQ[#] &], {n, 100}]

%o (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 Cf. A000010, A057660, A117494, A347104, A369687.

%Y Cf. also A369894, A369907, A369909.

%K nonn,easy

%O 1,4

%A _Wesley Ivan Hurt_, Jan 31 2024