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A163106
a(n) = sigma(sigma(tau(n))), where tau = number of divisors and sigma = sum of divisors.
2
1, 4, 4, 7, 4, 8, 4, 8, 7, 8, 4, 28, 4, 8, 8, 12, 4, 28, 4, 28, 8, 8, 4, 24, 7, 8, 8, 28, 4, 24, 4, 28, 8, 8, 8, 14, 4, 8, 8, 24, 4, 24, 4, 28, 28, 8, 4, 39, 7, 28, 8, 28, 4, 24, 8, 24, 8, 8, 4, 56, 4, 8, 28, 15, 8, 24, 4, 28, 8, 24, 4, 56, 4, 8, 28, 28, 8, 24, 4, 39, 12, 8, 4, 56, 8, 8, 8, 24, 4
OFFSET
1,2
COMMENTS
Repeated application of tau (number of divisors) and sigma (sum of divisors).
LINKS
FORMULA
MAPLE
with(numtheory) : A163106 := proc(n) sigma(sigma(tau(n))) ; end: seq(A163106(n), n=1..120) ; # R. J. Mathar, Jul 27 2009
MATHEMATICA
DivisorSigma[1, DivisorSigma[1, DivisorSigma[0, Range[90]]]] (* Harvey P. Dale, Oct 14 2017 *)
PROG
(PARI) A163106(n) = sigma(sigma(numdiv(n))); \\ Antti Karttunen, May 25 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jul 20 2009
EXTENSIONS
More terms from R. J. Mathar, Jul 27 2009
STATUS
approved