OFFSET
1,1
COMMENTS
Numbers k such that the number of distinct prime divisors of k is equal to the number of distinct prime divisors of the arithmetic derivative of k.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
MATHEMATICA
a[n_] := If[Abs@n < 2, 0, n Total[#2/#1 & @@@ FactorInteger[Abs@n]]];
Select[Range[100], PrimeNu[#] == PrimeNu[a[#]] &] (* G. C. Greubel, Apr 23 2017 *)
PROG
(PARI) arde(n) = sum(i=1, #f=factor(n)~, n/f[1, i]*f[2, i])
select(k->omega(k)==omega(arde(k)), vector(200, k, k+1))
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Jan 27 2017
STATUS
approved