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A163368
a(n) = phi(sigma(tau(n))).
1
1, 2, 2, 2, 2, 6, 2, 6, 2, 6, 2, 4, 2, 6, 6, 2, 2, 4, 2, 4, 6, 6, 2, 8, 2, 6, 6, 4, 2, 8, 2, 4, 6, 6, 6, 12, 2, 6, 6, 8, 2, 8, 2, 4, 4, 6, 2, 6, 2, 4, 6, 4, 2, 8, 6, 8, 6, 6, 2, 12, 2, 6, 4, 4, 6, 8, 2, 4, 6, 8, 2, 12, 2, 6, 4, 4, 6, 8, 2, 6, 2, 6, 2, 12, 6
OFFSET
1,2
LINKS
FORMULA
a(1) = 1, a(p) = 2 for p = primes (A000040), a(pq) = 6 for pq = product of two distinct primes (A006881), a(pq...z) = A000010(2^(k+1)-1) = A053287(k+1) for pq...z = product of k (k > 2) distinct primes p,q,...,z (A120944).
MAPLE
with(numtheory): A163368:=n->phi(sigma(tau(n))): seq(A163368(n), n=1..150); # Wesley Ivan Hurt, Dec 19 2016
MATHEMATICA
Table[EulerPhi[DivisorSigma[1, DivisorSigma[0, n]]], {n, 100}] (* G. C. Greubel, Dec 19 2016 *)
PROG
(PARI) vector(50, n, eulerphi(sigma(numdiv(n)))) \\ G. C. Greubel, Dec 19 2016
(Magma) [EulerPhi(SumOfDivisors(NumberOfDivisors(n))): n in [1..80]]; // Vincenzo Librandi, Dec 21 2016
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Jul 25 2009
STATUS
approved