# Matrix and Binomial Coefficients

Considering the construction of a matrix as follows.

The $n$th row in the matrix is filled with the coeffcients of $x^r$ in the expansion of $(1+x)^n$ from the columns $2n$ to $3n$ inclusive and circle all the numbers that are divisible by $n$ in the same row

How would I find the number of columns for which all the elements in a column are circled in the first j columns given j = 547 ?

-
Please don't post in the imperative mode (giving orders); if this is a homework assignment, please tag it using [homework]. Whether it is or not, you should say what you have done or where you are stuck, and please try to phrase your posts as questions, not orders. –  Arturo Magidin Jan 28 '11 at 14:41
@Arturo Modified the question. –  user6349 Jan 28 '11 at 14:44
"How would I find the number of columns for which all the elements in a column are circled in the first j columns given j = 547 ?" It feels that one of the "columns" must actually read "rows". Is the question correct? –  Srivatsan Jul 27 '11 at 22:59

Is the answer 547C2 where nCr = n!/(r!*(n-r)!) ? –  user6349 Jan 28 '11 at 15:03