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A163375 a(n) = sigma(tau(phi(n))). 2
1, 1, 3, 3, 4, 3, 7, 4, 7, 4, 7, 4, 12, 7, 7, 7, 6, 7, 12, 7, 12, 7, 7, 7, 12, 12, 12, 12, 12, 7, 15, 6, 12, 6, 15, 12, 13, 12, 15, 6, 15, 12, 15, 12, 15, 7, 7, 6, 15, 12, 12, 15, 12, 12, 15, 15, 13, 12, 7, 6, 28, 15, 13, 12, 18, 12, 15, 12, 12, 15, 15, 15 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A000203(A000005(A000010(n))) = A000203(A062821(n)) = A062069(A000010(n)).

MATHEMATICA

DivisorSigma[1, DivisorSigma[0, EulerPhi[Range[100]]]] (* G. C. Greubel, Dec 20 2016 *)

PROG

(PARI) vector(100, n, sigma(numdiv(eulerphi(n)))) \\ G. C. Greubel, Dec 20 2016

(MAGMA) [SumOfDivisors(NumberOfDivisors(EulerPhi(n))): n in [1..80]]; // Vincenzo Librandi, Dec 20 2016

CROSSREFS

Cf. A000005, A000010, A000203, A062069, A062821.

Sequence in context: A151664 A083503 A062069 * A027011 A267048 A326401

Adjacent sequences:  A163372 A163373 A163374 * A163376 A163377 A163378

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jul 25 2009

STATUS

approved

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Last modified September 30 21:27 EDT 2020. Contains 337440 sequences. (Running on oeis4.)