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:

USING: io kernel math.primes.factors prettyprint sequences ;

: semiprime? ( n -- ? ) factors length 2 = ;


100 <iota> [ semiprime? ] filter [ bl ] [ pprint ] interleave nl