Problem Statement

Semiprime numbers are natural numbers that are products of exactly two (possibly equal) prime numbers.

Semiprimes   are also known as:

(This particular number was chosen as the length of the Arecibo message).

Write a function determining whether a given number is semiprime.

Let's start with the solution:

  [ primefactors size 2 = ] is semiprime ( n --> b )

  say "Semiprimes less than 100:" cr
  100 times [ i^ semiprime if [ i^ echo sp ] ]