A162964 a(n) = sigma(sigma(sigma(sigma(sigma(n))))).

1, 15, 24, 60, 120, 360, 168, 480, 168, 360, 360, 1170, 480, 1512, 1512, 210, 360, 1170, 728, 1680, 576, 480, 1512, 4800, 210, 1680, 1344, 3276, 992, 2016, 576, 1651, 1560, 3276, 1560, 1512, 1512, 4800, 3276, 4064, 1680, 5952, 1560, 5040, 4800, 2016, 1560, 5040

Offset: 1

Author

Jaroslav Krizek, Jul 19 2009

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A129076, A066971, A051027.

Cf. also A049107.

Programs

Maple

with(numtheory); f:=n->sigma(sigma(sigma(sigma(sigma(n))))); [seq(f(n),n=1..100)];

Mathematica

Table[Nest[DivisorSigma[1,#]&,n,5],{n,50}] (* Harvey P. Dale, Apr 19 2013 *)

PARI

A162964(n) = sigma(sigma(sigma(sigma(sigma(n))))); \\ Antti Karttunen, Nov 18 2017

Formula

a(n) = A000203(A000203(A000203(A000203(A000203(n))))).

Extensions

More terms from N. J. A. Sloane, Mar 20 2010