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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
OFFSET
1,2
COMMENTS
LINKS
FORMULA
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
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, May 27 2007
STATUS
approved