Problem Statement

A number is an   attractive number   if the number of its prime factors (whether distinct or not) is also prime.

The number   20,   whose prime decomposition is   2 × 2 × 5,   is an   attractive number   because the number of its prime factors   (3)   is also prime.

Show sequence items up to   120.

Let's start with the solution:

 [ primefactors size
   primefactors size 1 = ] is attractive ( n --> b )

120 times 
  [ i^ 1+ attractive if 
      [ i^ 1+ echo sp ] ]