# summation problem

• January 20th 2010, 03:27 PM
dynamo
summation problem
hi guys,is there a closed formula for the following sort of expression
( sigma from 1 to n)( sigma from 1 to j=n)( sigma from 1 to i=j)....x
the phrases in brackets should be substituted by sigma symbols described.Thanks for any help.
• January 20th 2010, 04:07 PM
Krizalid
Quote:

Originally Posted by dynamo
hi guys,is there a closed formula for the following sort of expression
( sigma from 1 to n)( sigma from 1 to j=n)( sigma from 1 to i=j)....x

What does $x\ldots$ stand for?
• January 21st 2010, 07:47 AM
dynamo
x is what gets incremented
x is what gets incremented.For instance it starts out at x=1 then x=2 then x=3 when we have summation of x from x=1 to n.my question is equivalent to the following loop
for(int i=1;i<n;i++){
for(j=1;j<i;j++){
for(k=1;k<j;k++){
.
.
.
x=x+1;
.
.
.
}
}
}
thankx.