Goldbach Conjecture

The Goldbach conjecture is a still unproved proposition that any even integer (strictly greater than 2) can be written as the sum of 2 prime numbers.

Example: Decompositions in sum of 2 prime numbers: 4 = 2 + 2, 10 = 3 + 7 = 5 + 5, and so on.

Informatically, it is verified for all the even integers up to one billion of billion (and surely more advantage today because calculations are still in progress).

The program is limited to even integers less than 10^9 and also limited in number of decompositions.

As the name suggests it is a conjecture, so to date it has no mathematical demonstration. Mathematicians suppose it to be true, and it is computer-verified up to very large numbers, but it does not prove that it is true for all numbers.

The algorithm is similar to that of a prime factors decomposition. It is possible to speed up the calculations by using an already calculated list of prime numbers.

// Javascript limited to n = 200
var pr = new Array(3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97);
function goldback(n) {
for (p in pr) {
if (pr[p] <= n/2 && in_array(n-pr[p], pr)) {
return n+=+pr[p]+++(n-pr[p]);
}
}
}