Mathematical notation in algorithms

Question

I am currently reading the Algorithm Design Manual, but my mathematical notation has become a little rusty.

What does

mean?

Answer 1

Binomial coefficient? (also, see combination)

Answer 2

It means "n choose k", or in this case, "a choose b". It is a shorthand for the formula a!/(b!((a-b)!)).

Sorry for the many parenthesis, just didn't want amibuity. ! means factorial, 5! = 5*4*3*2*1, etc.

It is used for binomial expansion, and Pascal's Triangle.

Answer 3

Combination is the first thing that comes to mind...but without context, there are probably other meanings for the same notation.