if (sizeInBits < 100) {
            rounds = 50;
            rounds = n < rounds ? n : rounds;
            return this.passesMillerRabin(rounds, random);
        } else {
            if (sizeInBits < 256) {
                rounds = 27;
            } else if (sizeInBits < 512) {
                rounds = 15;
            } else if (sizeInBits < 768) {
                rounds = 8;
            } else if (sizeInBits < 1024) {
                rounds = 4;
            } else {
                rounds = 2;
            }

            rounds = n < rounds ? n : rounds;
            return this.passesMillerRabin(rounds, random) && this.passesLucasLehmer();
        }

this.passesMillerRabin(rounds, random) && this.passesLucasLehmer();

    /**
     * Returns {@code true} if this BigInteger is probably prime,
     * {@code false} if it's definitely composite.
     *
     * This method assumes bitLength > 2.
     *
     * @param  certainty a measure of the uncertainty that the caller is
     *         willing to tolerate: if the call returns {@code true}
     *         the probability that this BigInteger is prime exceeds
     *         {@code (1 - 1/2<sup>certainty</sup>)}.  The execution time of
     *         this method is proportional to the value of this parameter.
     * @return {@code true} if this BigInteger is probably prime,
     *         {@code false} if it's definitely composite.
     */
    boolean primeToCertainty(int certainty, Random random) {
        int rounds = 0;
        int n = (Math.min(certainty, Integer.MAX_VALUE-1)+1)/2;

        // The relationship between the certainty and the number of rounds
        // we perform is given in the draft standard ANSI X9.80, "PRIME
        // NUMBER GENERATION, PRIMALITY TESTING, AND PRIMALITY CERTIFICATES".
        int sizeInBits = this.bitLength();
        if (sizeInBits < 100) {
            rounds = 50;
            rounds = n < rounds ? n : rounds;
            return passesMillerRabin(rounds, random);
        }

        if (sizeInBits < 256) {
            rounds = 27;
        } else if (sizeInBits < 512) {
            rounds = 15;
        } else if (sizeInBits < 768) {
            rounds = 8;
        } else if (sizeInBits < 1024) {
            rounds = 4;
        } else {
            rounds = 2;
        }
        rounds = n < rounds ? n : rounds;

        return passesMillerRabin(rounds, random) && passesLucasLehmer();
    }

Python 2.7.11 (v2.7.11:6d1b6a68f775, Dec  5 2015, 20:40:30) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> pp = 55
>>> p = 2*pp - 1
>>> t = p - 1
>>> t = t / 2;
>>> print (t)
54
>>>

>>> pp = 55
>>> p = 2**pp - 1
>>> t = p - 1
>>> t = t / 2;
>>> print (t)
18014398509481983