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%I #6 Dec 19 2020 08:00:07
%S 1,1,2,2,4,4,8,8,6,6,12,12,24,24,48,48,10,10,20,20,40,40,80,80,60,60,
%T 120,120,240,240,480,480,12,12,24,24,48,48,96,96,72,72,144,144,288,
%U 288,576,576,120,120,240,240,480,480,960,960,720,720,1440,1440,2880,2880,5760,5760,16,16,32,32,64,64,128,128
%N a(n) = phi(A019565(n)), where phi is Euler totient function.
%F If 2n = 2^e1 + 2^e2 + ... + 2^ek [e1 ... ek distinct], then a(n) = A006093(e1) * A006093(e2) * ... * A006093(ek).
%F a(n) = A000010(A019565(n)).
%o (PARI) A339820(n) = { my(m=1, p=1); while(n>0, p = nextprime(1+p); if(n%2, m *= (p-1)); n >>= 1); (m); };
%Y Cf. A000010, A019565, A339821 (bisection).
%Y Cf. also A324650, A339809.
%K nonn
%O 0,3
%A _Antti Karttunen_, Dec 18 2020
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