mersenne.a60

b̲e̲g̲i̲n̲
    i̲n̲t̲e̲g̲e̲r̲ p̲r̲o̲c̲e̲d̲u̲r̲e̲ mersenne(n); v̲a̲l̲u̲e̲ n; i̲n̲t̲e̲g̲e̲r̲ n; b̲e̲g̲i̲n̲
        i̲n̲t̲e̲g̲e̲r̲ i, m;
        m := 1;
        f̲o̲r̲ i := 1 s̲t̲e̲p̲ 1 u̲n̲t̲i̲l̲ n d̲o̲
            m := m * 2;
        mersenne := m - 1;
    e̲n̲d̲;

    B̲o̲o̲l̲e̲a̲n̲ p̲r̲o̲c̲e̲d̲u̲r̲e̲ isprime(n); v̲a̲l̲u̲e̲ n; i̲n̲t̲e̲g̲e̲r̲ n; b̲e̲g̲i̲n̲
        i̲f̲ n < 2 t̲h̲e̲n̲
            isprime := f̲a̲l̲s̲e̲
        e̲l̲s̲e̲ i̲f̲ entier(n / 2) * 2 = n t̲h̲e̲n̲
            isprime := (n = 2)
        e̲l̲s̲e̲ b̲e̲g̲i̲n̲
            c̲o̲m̲m̲e̲n̲t̲ - check odd divisors up to sqrt(n);
            i̲n̲t̲e̲g̲e̲r̲ i, limit;
            B̲o̲o̲l̲e̲a̲n̲ divisible;
            limit := entier(sqrt(n));
            divisible := f̲a̲l̲s̲e̲;
            f̲o̲r̲ i := 3, i+2 w̲h̲i̲l̲e̲ i ≤ limit ∧ ¬ divisible d̲o̲ b̲e̲g̲i̲n̲
                i̲f̲ entier(n / i) * i = n t̲h̲e̲n̲
                    divisible := t̲r̲u̲e̲;
                i := i + 2
            e̲n̲d̲;
            isprime := i̲f̲ divisible t̲h̲e̲n̲ f̲a̲l̲s̲e̲ e̲l̲s̲e̲ t̲r̲u̲e̲
        e̲n̲d̲
    e̲n̲d̲;

    c̲o̲m̲m̲e̲n̲t̲ - main code begins here;
    i̲n̲t̲e̲g̲e̲r̲ i, m;
    PRINTTEXT(`Searching to M(19) for Mersenne primes');
    NLCR;
    f̲o̲r̲ i := 1 s̲t̲e̲p̲ 1 u̲n̲t̲i̲l̲ 19 d̲o̲ b̲e̲g̲i̲n̲
        m := mersenne(i);
        i̲f̲ isprime(m) t̲h̲e̲n̲ b̲e̲g̲i̲n̲
            PRINTTEXT(`M(');
            print(i);
            PRINTTEXT(`) : ');
            print(m);
            NLCR
        e̲n̲d̲
    e̲n̲d̲
e̲n̲d̲