a_1 = sigma ( -i ) for i=1..n {or -(n+1)*n/2 }
a_n-1 = sigma ( PI {-i} for i=1..j-1 X PI {-i} for i=j+1..n ) for j=1..n
you need a script/algo to calculate this even for a_n-1
a_n-k = sigma (choose subset k out of n) PI (k elements)
you need some functions:
1. subset_k_n (input n input k input start input prev_subset output next_subset output last)
2. PI_subset (input subset_array output subset_product)
3. SIGMA
3.1 calls subset_k_n with start=1
3.2 subset_k_n return with the 1st subset (1..k) = prev_subset
3.3 calls PI_subset with (1..k)
3.4 PI_subset return with k(k+1)/2
3.5 SIGMA set this value as a_n-k
3.6 call subset_k_n with prev_subset
3.7 call PI_subset with the new subset
3.8 add a_n-k the returned value from PI_subset
3.9 goto 3.6 until subset_k_n->stop = 1
As a web developer or IT admin, successfully managing multiple client accounts can be challenging. In this webinar we will look at the tools provided by Media Temple and Plesk to make managing your clients’ hosting easier.
see this link
http://en.wikipedia.org/wiki/Pascal's_triangle