Questions tagged [pseudoprimes]

Pseudoprimes are composite numbers which pass some primality test - a property that is always true for prime numbers. This may be Fermat's Little Theorem for one base or many, or some other test.

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Showing numbers are Carmichael Numbers

I'm currently working through a problem set for mathematical cryptography and came across a question which asks: Say why $676, 75, 143$ are not Carmichael Numbers Furthermore, explain why ...
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Fermat's test to prove pseudoprimes

I'm self teaching myself number theory as I'm doing a course in cryptography and anything I've found hasn't helped. The question I'm stuck on is: Use Fermat Test to show 19 is a pseudoprime base 3 ...
Question: Show that every composite Fermat number $F_m=2^{2^m}+1$ is a pseudoprime base 2. Hint: Raise the congruence $2^{2^m}\equiv-1($mod $F_m)$ to the $2^{2^m-m}$th power. Even with the hint, I'm ...
Why is $561$ missing from this list?
On the MathWorld page: http://mathworld.wolfram.com/FermatPseudoprime.html in the first table, I expect to see $561$ on every line, but it is not on the line for base $3$. When you click on the ...