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A163105
a(n) = tau(sigma(tau(n))), where tau = number of divisors of n (A000005), and sigma = sum of divisors of n (A000203).
1
1, 2, 2, 3, 2, 2, 2, 2, 3, 2, 2, 6, 2, 2, 2, 4, 2, 6, 2, 6, 2, 2, 2, 4, 3, 2, 2, 6, 2, 4, 2, 6, 2, 2, 2, 2, 2, 2, 2, 4, 2, 4, 2, 6, 6, 2, 2, 6, 3, 6, 2, 6, 2, 4, 2, 4, 2, 2, 2, 6, 2, 2, 6, 4, 2, 4, 2, 6, 2, 4, 2, 6, 2, 2, 6, 6, 2, 4, 2, 6, 4, 2, 2, 6, 2, 2, 2, 4, 2, 6, 2, 6, 2, 2, 2, 6, 2, 6, 6, 2, 2, 4, 2, 4, 4
OFFSET
1,2
COMMENTS
Repeated application of tau (number of divisors) and sigma (sum of divisors).
FORMULA
MAPLE
with(numtheory) : A163105 := proc(n) tau(sigma(tau(n))) ; end: seq(A163105(n), n=1..120) ; # R. J. Mathar, Jul 27 2009
MATHEMATICA
With[{s = DivisorSigma}, s[0, s[1, s[0, Range[100]]]]] (* Paolo Xausa, Oct 07 2024 *)
PROG
(PARI) A163105(n) = numdiv(sigma(numdiv(n))); \\ Antti Karttunen, Jul 23 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jul 20 2009
EXTENSIONS
More terms from R. J. Mathar, Jul 27 2009
Name edited by Antti Karttunen, Jul 23 2017
STATUS
approved