You are experiencing integer overflow. Take a look at BigInteger for one workaround.

Array of Fibonacci values; Value of high index turns array value into negative
I am Making a Power Supply, There is a 40v rail that needs a 10000uf cap, I was wondering if it is safe to use a 50v rated cap, Should i be worried that it is close to the Limit? The Brand of the capacitor is Elna. 
