A163106 a(n) = sigma(sigma(tau(n))), where tau = number of divisors and sigma = sum of divisors.

1, 4, 4, 7, 4, 8, 4, 8, 7, 8, 4, 28, 4, 8, 8, 12, 4, 28, 4, 28, 8, 8, 4, 24, 7, 8, 8, 28, 4, 24, 4, 28, 8, 8, 8, 14, 4, 8, 8, 24, 4, 24, 4, 28, 28, 8, 4, 39, 7, 28, 8, 28, 4, 24, 8, 24, 8, 8, 4, 56, 4, 8, 28, 15, 8, 24, 4, 28, 8, 24, 4, 56, 4, 8, 28, 28, 8, 24, 4, 39, 12, 8, 4, 56, 8, 8, 8, 24, 4

Offset

1,2

Comments

Repeated application of tau (number of divisors) and sigma (sum of divisors).

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Formula

a(n) = A000203(A000203(A000005(n))) = A000203(A062069(n)) = A051027(A000005(n)).

Maple

with(numtheory) : A163106 := proc(n) sigma(sigma(tau(n))) ; end: seq(A163106(n), n=1..120) ; # R. J. Mathar, Jul 27 2009

Mathematica

DivisorSigma[1, DivisorSigma[1, DivisorSigma[0, Range[90]]]] (* Harvey P. Dale, Oct 14 2017 *)

Prog

(PARI) A163106(n) = sigma(sigma(numdiv(n))); \\ Antti Karttunen, May 25 2017

Crossrefs

Cf. A000005, A000203, A051027, A062069.

Sequence in context: A053510 A197009 A204156 * A331619 A374104 A258972

Adjacent sequences: A163103 A163104 A163105 * A163107 A163108 A163109

Keyword

nonn

Author

Jaroslav Krizek, Jul 20 2009

Extensions

More terms from R. J. Mathar, Jul 27 2009

Status

approved