generate a summation series

3(2+1)+4(3+2+1)+5(4+3+2+1)+6(5+...1)+...+1000(999+...+1).

How to write a matlab code to calculate the following summation without using for loop?

i can see the trend for 3(2+1) if the n = 1 (n+2)[((n+2)-1)+((n+2)-2)].

Assume the summation only sum until 6th term.

can we use array to solve this?

[ibraheem kanai]

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

(My internal tracking number for @ibraheem kanai query is T0098905)

Answer 1

[Stephen23]

>> X = 1+cumsum(2:999); % 1+[2,3+2,4+3+2,...,999+..+2]
>> Y = 3:1000;          % [3,4,5,...,1000]
>> sum(X.*Y)
ans =   125083208248

Note that this uses element-wise multiplication.

[Odien]

Thank you !

[Walter Roberson]

This looks like it was homework to me...

Answer 2

[Walter Roberson]

It does have a symbolic answer that you could find using nested symsum() if you have the symbolic toolbox.

But for a numeric answer: cumsum() and multiply by something gives a bunch of terms...