Euler problem 31

In England the currency is made up of pound, £, and pence, p, and there are eight coins in general circulation:

1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) and £2 (200p).

It is possible to make £2 in the following way:

1£1 + 150p + 220p + 15p + 12p + 31p

How many different ways can £2 be made using any number of coins?

performance improvements:

1) Eliminate coin order (int i = 0 -> i = j)                 // ∞∞ -> 59 ms.
2) Stop substracting 1 pence (i<coins.Length -> i<7)  // 59 ->  1 ms.

problem31 =       73682 elapsed time:    1 ms. Test Passed.