FactorsOf2Powers.jl

#Factoroidaan 2^(q-2) - 1 alkulukutekijoiksi p
# ehtona  q % 8 = 1,7
# tutkitaan toteuttaako n=p*q kongruenssin 2^(n-2)=1 (mod n)
using Primes
function alkutekijat(q1::Int,q2::Int)
    for q in q1 : 2 : q2
        res = q % 8
        if (res==1) || (res==7)
            a = factor(Vector,big(2)^(q-2)-1) #alkulukutekijät
            println("q = ",q," , ",a)
            for k in 1 : length(a)
                res = a[k] % 8
                if (res == 1) || (res == 7)
                    n = big(q * a[k])
                    if powermod(2,n-2,n) == 1
                        println("q = ",q, " p = ",a[k],"  n = ",n,"  kongruenssi")
                    end
                end
            end
        end
    end
end