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A229341
a(n) = tau(n'), the number of divisors of the arithmetic derivative of n.
4
1, 1, 3, 1, 2, 1, 6, 4, 2, 1, 5, 1, 3, 4, 6, 1, 4, 1, 8, 4, 2, 1, 6, 4, 4, 4, 6, 1, 2, 1, 10, 4, 2, 6, 12, 1, 4, 5, 6, 1, 2, 1, 10, 4, 3, 1, 10, 4, 6, 6, 8, 1, 5, 5, 6, 4, 2, 1, 6, 1, 4, 4, 14, 6, 2, 1, 12, 4, 2, 1, 12, 1, 4, 4, 10, 6, 2, 1, 10, 12, 2, 1, 6, 4, 6
OFFSET
2,3
LINKS
FORMULA
a(n) = A000005(A003415(n)).
EXAMPLE
For n=4, tau(n')=tau(4)=3.
For n=5, tau(n')=tau(1)=1.
MATHEMATICA
dn[0] = 0; dn[1] = 0; dn[n_?Negative] := -dn[-n]; dn[n_] := Module[{f = Transpose@ FactorInteger@ n}, If[PrimeQ@n, 1, Total[n*f[[2]]/f[[1]]]]]; (* see A003415 *); f[n_] := DivisorSigma[0, dn@ n]; Array[f, 85, 2] (* Robert G. Wilson v, Mar 12 2018 *)
PROG
(PARI) rd(n) = {local(fac); if(n<1, 0, fac=factor(n); sum(i=1, matsize(fac)[1], n*fac[i, 2]/fac[i, 1]; )); }
a(n) = numdiv(rd(n)); \\ Michel Marcus, Sep 24 2013
(GAP) List(List(List([2..10^2], Factors), i->Product(i)*Sum(i, j->1/j)), Tau); # Muniru A Asiru, Mar 05 2018
CROSSREFS
Sequence in context: A008296 A351397 A140185 * A372245 A106790 A078897
KEYWORD
nonn
AUTHOR
Luca Brigada Villa, Sep 24 2013
STATUS
approved