Combination is not the term, I guess you mean permutations and it is 50! = 3.04140932*10^64 which you can't store it anywhere not just because of capacity problems but also because of the time required for writing them, it would take billions times the galaxy's age for a multiple penta byte per second write operation, I suppose.
you are wrong... permutations are only for cases where the sequence is not a factor like when you draw 5 cards from a 52 cards deck... it doesnt matter if you draw spade ace first or last... so As-2s-3s-4s-5s is the exact same as 5s-3s-2s-4s-As....
No, you are wrong.
Permutation IS about the cases
sensitive to order. We say: "What permutations we could have for 5 cards"?
This is order sensitive and is 5!= 120 i.e. we got 5 cards and we can arrange them in 120 different ways.
Combination is used for a very different scenarios, e.g. how many different hands(each with 5 cards) we can draw from a 52 cards deck? Here the answer is 52!/47!/5! = 52*51*50*49*48/5/4/3/2=2,598,960 different hands.
So, when you ask about
combinations usually you have to give 2 numbers like 5 and 52 in my example, i.e.
5 of 52.
Now I understand you are asking about
permutation with repetition for 50 placements of 51 characters. Which is obviously 51^50, but you should never use the term
combination for expressing it because in math (and I'm not a mathematician by the way) we use this term a bit different with colloquial language.