A129076 a(n) = sigma(sigma(sigma(sigma(n)))), where sigma(n) = sum of divisors of n.

1, 8, 15, 24, 56, 120, 60, 168, 60, 120, 120, 360, 168, 480, 480, 104, 120, 360, 252, 728, 210, 248, 480, 1512, 104, 728, 546, 1170, 336, 992, 210, 576, 504, 1170, 504, 480, 480, 1512, 1170, 1344, 728, 1680, 504, 1560, 1512, 992, 504, 1560, 384, 432, 992, 588

Offset

1,2

Comments

a(n) = A000203(A000203(A051027(n))) = A051027(A000203(A000203(n))) = A000203(A051027(A000203(n))) = A000203(A066971(n)) = A066971(A000203(n)) = A051027(A051027(n)). - Jaroslav Krizek, Jul 19 2009

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

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

Mathematica

Nest[DivisorSigma[1, #]&, Range[60], 4] (* Harvey P. Dale, Oct 05 2011 *)

Prog

(Magma) [ SumOfDivisors(SumOfDivisors(SumOfDivisors(SumOfDivisors(n)))) : n in [1..100]];
(PARI) a(n) = sigma(sigma(sigma(sigma(n)))); \\ Michel Marcus, Apr 29 2017

Crossrefs

Cf. A000203, A051027, A066971.

Cf. A019293.

Sequence in context: A034104 A034114 A069826 * A292949 A072177 A169875

Adjacent sequences: A129073 A129074 A129075 * A129077 A129078 A129079

Keyword

easy,nonn

Author

Jonathan Vos Post, May 27 2007

Status

approved