The thing about scoring mutiples (pairs, 3-of-a-kind, 4-of-a-kind) in cribbage is that it all just breaks down to scoring pairs. 3-of-a-kind is worth 6 points because there are 3-choose-2 pairs (which is 3) in a 3-of-a-kind. Each pair being worth 2 points yields 6 points total. So, using similar techniques as stated already in this thread, one can generate the set of all pairs and if the two elements in the pair are the same, increment the count of pairs.