A066971 a(n) = sigma(sigma(sigma(n))).

1, 7, 8, 15, 28, 56, 24, 60, 24, 56, 56, 120, 60, 168, 168, 63, 56, 120, 96, 252, 104, 112, 168, 480, 63, 252, 234, 360, 195, 336, 104, 210, 224, 360, 224, 248, 168, 480, 360, 546, 252, 728, 224, 504, 480, 336, 224, 504, 186, 255, 336, 260, 360, 1170, 336, 1170

Offset: 1

Author

Benoit Cloitre, Jan 26 2002

Keywords

• nonn

Comments

a(n) = A000203(A000203(A000203(n))) = A000203(A051027(n)) = A051027(A000203(n)). - Jaroslav Krizek, Jul 19 2009

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000203, A051027.

Programs

Mathematica

lst={};Do[AppendTo[lst,DivisorSigma[1,DivisorSigma[1,DivisorSigma[1,n]]]],{n,5!}];lst (* Vladimir Joseph Stephan Orlovsky, Mar 11 2009 *)
Table[Nest[DivisorSigma[1,#]&,n,3],{n,60}] (* Harvey P. Dale, Apr 06 2023 *)

PARI

a(n) = { sigma(sigma(sigma(n))) } \\ Harry J. Smith, Apr 12 2010