1,2

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

Antti Karttunen, Table of n, a(n) for n = 1..16384

Index entries for sequences related to sigma(n)

a(n) = A000203(A000005(A000203(n))) = A000203(A062068(n)) = A062069(A000203(n)).

with(numtheory) : A163108 := proc(n) sigma(tau(sigma(n))) ; end: seq(A163108(n), n=1..120) ; # R. J. Mathar, Jul 27 2009

(PARI) A163108(n) = sigma(numdiv(sigma(n))); \\ Antti Karttunen, Nov 18 2017

Cf. A000005, A000203, A062068, A062069, A163107.

Sequence in context: A127737 A299416 A333974 * A077005 A328347 A265723

Adjacent sequences: A163105 A163106 A163107 * A163109 A163110 A163111

nonn

Jaroslav Krizek, Jul 20 2009

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

approved