Using one deck of cards.
Taking into account different suites. However, the way they are arranged would not be accounted for. Ace of Spades and Queen of Diamonds would be the same as Queen of Diamonds and Ace of Spades.
Pictures (Jacks, Queens, Kings) = 10
Aces = 11, or 1
The way I see it, 21 can be split into:
20 + 1, 19 + 2, 18 + 3 ... 1 + 20. Each of those numbers can further be split down. It appears to be kind of recursive?
Then we have 2-card ways, 3-card ways, 4-card ways and so on ...
It seems to me a very, very tough problem and I have no idea how to approach it. Any ideas?