## Exercise I

Posted 02/23/2015
Refresh the webpage if formulas are not shown correctly.
--------------------------
Previous    Next
--------------------------

A monomial is a polynomial wich has only one term with 1 as coefficient. The degree of a monomial is the sum of degrees of all the variables.

For example, x^2yz^3 is a monomial of degree 6.

a(n) is the number of monomials of degree at most n in n variables.

For example, a(2)=6 because we have monomials 1, x_1, x_2, x_1x_2, x_1^2 and x_2^2.

Find a(n).