# Tagged Questions

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### Number of sequences with n digits, even number of 1's (Continued question)

Some guy asked a very interesting question here before. He was trying to figure out a formula to calculate $a_n$ number of sequences with n digits from $\{1,2,3,4\}$ and an even number of 1's. Which ...
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### Let Cn denote the number of ways of writing a valid list of open and closed parentheses of length 2n

(a) Let Cn denote the number of ways of writing a valid list of open and closed parentheses of length 2n (valid means that at any point along the list, the number of open parentheses must be greater ...
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### How many partitions are there?

How many partitions are there for $\{1,\cdots,100\}$ for $3$ sets, $A,B,C$, such that $A$ cannot contain consecutive numbers ($\left|a-b\right|=1$) Anyway, I thought about using recurrence ...
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### Prove this recurrence relation? (catalan numbers)

$$C_0 = 1,\quad C_{n+1} = C_0C_n + C_1C_{n−1}+ \cdots + C_kC_{n−k} + \cdots + C_nC_0\text{ ?}$$ Where Cn denotes the number of ways of writing a valid list of open and closed parentheses of length ...
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### Divide and Conquer (recurrence relation problem)…

The problem: (a) Use a divide-and-conquer approach to devise a procedure to find the largest and next-to-largest numbers in a set of n distinct integers. (b) Give a recurrence relation for ...
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