29 lines
887 B
Plaintext
29 lines
887 B
Plaintext
Semiprime numbers are natural numbers that are products of exactly two (possibly equal) [[prime_number|prime numbers]].
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'''Semiprimes''' are also known as:
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:::* '''semi-primes'''
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:::* '''biprimes'''
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:::* '''bi-primes'''
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:::* ''' ''2-almost'' ''' primes
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:::* or simply: ''' ''P<sub>2</sub> '' '''
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;Example:
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<big> 1679 = 23 × 73 </big>
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(This particular number was chosen as the length of the [http://en.wikipedia.org/wiki/Arecibo_message Arecibo message]).
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;Task:
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Write a function determining whether a given number is semiprime.
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;See also:
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* The Wikipedia article: [[wp:Semiprime|semiprime]].
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* The Wikipedia article: [[wp:Almost_prime|almost prime]].
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* The OEIS sequence: [[oeis:A001358|A001358: semiprimes]] which has a shorter definition: ''the product of two primes''.
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<br><br>
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