Combinations with a certain number of symbol repetitions

Asked Mar 26 '17 at 22:43

Active Mar 27 '17 at 07:59

Viewed 27 times

Help please formulate a formula for calculating the number of all possible combinations for these conditions:

The string must contain the a certain number of characters (no more, no less )!
Symbol A - 2 count
Symbol B - 3 count
Note: characters and their count can be more than two (for example, C-1, D-2, E-32, etc)

I sketched all the combinations manually for an example:

aabbb
abbba
bbbaa
bbaab
baabb
abbab
ababb
babba
babab
bbaba

edited Mar 27 '17 at 07:59

asked Mar 26 '17 at 22:43

Viaches

Hint: Choose positions for the A's; from the remaining positions, choose positions for the B's. Continue. – N. F. Taussig Mar 26 '17 at 23:12
@Misha, Thank you very much, you're right, I missed it! – Viaches Mar 27 '17 at 07:58

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