perplexus.info :: Just Math : Getting 13

Getting 13 (Posted on 2014-07-21)

Using integers 1,2,3 & 4 only , in how many distinct ways a sum of 13 can be achieved?

Rem: The order matters i.e. 1,4,4; 4,1,4; & 4,4,1 are considered distinct.

Submitted by Ady TZIDON

Rating: 4.0000 (1 votes)

Solution: (Hide)

Let f(n) = number of ways of achieving total n.
f(0)=1 f(1)=2 and the recursion formula is:
f(n) = f(n-4) + f(n-3) + f(n-2) + f(n-1).
f(13) = 2872

See Steve Herman detailed soltion.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
re: comparing two approaches	Steve Herman	2014-07-22 16:05:18
re: Solution @ tomarkin	Ady TZIDON	2014-07-22 10:12:31
comparing two approaches	Ady TZIDON	2014-07-22 10:05:47
Elegant(?) approach	Steve Herman	2014-07-21 19:17:46
Solution	tomarken	2014-07-21 16:31:11

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