A061884 - OEIS

%I #18 Jul 05 2024 18:14:42

%S 1,2,4,5,8,8,12,12,14,16,20,20,24,24,32,26,32,28,36,40,48,40,44,48,44,

%T 48,48,60,56,64,60,56,80,64,96,70,72,72,96,96,80,96,84,100,112,88,92,

%U 104,90,88,128,120,104,96,160,144,144,112,116,160,120,120,168,116,192

%N a(n) = Sum_{ d | n } phi(lcm(d,n/d)), where phi(n) = Euler totient A000010.

%H Alois P. Heinz, <a href="/A061884/b061884.txt">Table of n, a(n) for n = 1..20000</a>

%p A061884 := proc(n) local b,d: b := 0; for d from 1 to n do if irem(n,d)=0 then b := b+phi(lcm(d,n/d)); fi; od; RETURN(b); end:

%t Table[Plus @@ Map[ EulerPhi[LCM[ #, n/# ]] &, Select[ Range@n, (Mod[n, # ] == 0) &]], {n, 65}] (* _Robert G. Wilson v_, Sep 30 2006 *)

%o (PARI) a(n)=sumdiv(n,d,eulerphi(lcm(d,n/d))) \\ _Charles R Greathouse IV_, Feb 21 2013

%Y Cf. A000010, A001616, A057670, A007427.

%K easy,nonn

%O 1,2

%A _Vladeta Jovovic_, May 12 2001