Well, good luck then. Be aware that there are 456976 possible combinations with words of length 4 (using the 26 letters of the English alphabet), and 308915776 words of length 6. The latter will take about 5.75Gb to store. If you want ngrams up to 8 characters, look around for a box with 3.7Tb of memory. And if you need to go to ngrams of length 12, you'd be looking at more than 1.5 Eb.