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A129076 a(n) = sigma(sigma(sigma(sigma(n)))), where sigma(n) = sum of divisors of n. 3
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 22 23:50 EST 2022. Contains 350504 sequences. (Running on oeis4.)