If a_n= 2^n / (2n)! then simplify it..?

Wikkivahi,

I am ready to help you out solving this sum, but I can't make out the what does a_n stand for and what does 2^n mean, even as (2n)! Stands for factorial of 2n as a whole, I suppose. Is not it? Please explain the a_n or is it simply one representation?

I wait for your clarification.

Kahani, a_n means the nth term in the sequence. In other words, the first number in the sequence is a_1 = 2^1/2! The second number is a_2 = 2^2/4! The nth number is a_n = 2^n/(2n)!

The ^ notation means superscript (i.e. an exponent). 2^2 means "two squared". 2^n means "two to the nth power".

a_n =

2^n =

I'll let you work on the problem first, since you said you're ready to solve it. :)