A229341 - OEIS

%I #49 Mar 26 2018 20:59:27

%S 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,

%T 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,

%U 12,4,2,1,12,1,4,4,10,6,2,1,10,12,2,1,6,4,6

%N a(n) = tau(n'), the number of divisors of the arithmetic derivative of n.

%H Antti Karttunen, <a href="/A229341/b229341.txt">Table of n, a(n) for n = 2..65537</a>

%F a(n) = A000005(A003415(n)).

%e For n=4, tau(n')=tau(4)=3.

%e For n=5, tau(n')=tau(1)=1.

%t 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 *)

%o (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];));}

%o a(n) = numdiv(rd(n)); \\ _Michel Marcus_, Sep 24 2013

%o (GAP) List(List(List([2..10^2],Factors),i->Product(i)*Sum(i,j->1/j)),Tau); # _Muniru A Asiru_, Mar 05 2018

%Y Cf. A000005, A003415.

%K nonn

%O 2,3

%A _Luca Brigada Villa_, Sep 24 2013