Which of the following integers can be used to prove that 403 is composite using the Solovay-Strassen primality test ?
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Let's check the numbers using Solovay-Strassen primality test .
Let's start with 201. The Solovay- Strassen primality test says that if ( a / n ) ≢ a 2 n − 1 ( m o d n ) , (a is an integer coprime to n), then n is a composite number. Now let's look how it works with 201: We have to compute 201^201 mod 403 because (403-1)/2 = 201.
( 2 0 1 ) 2 0 1 = ( ( 2 0 1 ) 3 ) ) 6 7 ≡ ( 1 5 1 ) 6 7 = 1 5 1 ∙ ( ( 1 5 1 ) 2 ) 3 3 ≡ 1 5 1 ∙ ( 2 3 3 ) 3 3 = 1 5 1 ∙ ( ( 2 3 3 ) 3 ) 1 1 ≡ 1 5 1 ∙ 3 7 6 1 1 = 1 5 1 ∙ 3 7 6 ∙ ( ( 3 7 6 ) 2 ) 5 ≡ 3 5 6 ∙ ( 3 2 6 ) 5 = 3 5 6 ∙ ( 3 2 6 ) 3 ∙ ( 3 2 6 ) 2 ≡ 3 5 6 ∙ 6 6 ∙ 2 8 7 = 6 7 4 3 3 5 2 ≡ 3 5 6 ( m o d 4 0 3 )
We got the remainder 356 and it can't be equal to Jacobi symbol. So the answer is 201 .