Find the sum `sumsum_(0lt=ilt=jlt=n)^ nC_i^n C_j`

Find the sum sumsum_(0leiltjlen)"^nC_i

Find the sum sumsum_(0leiltjlen) "^nC_i "^nC_j

Find the value of sumsum_(0lt=i

Find the sumsum_(0leiltjlen)1 .

Find the sum sumsum_(i!=j)^ nC_i^n C_j

If (1+x)^n=C_0+C_1x+C_2x^2+.......+C_n x^n , then show that the sum of the products of the coefficients taken two at a time, represented by sumsum_(0lt=iltjlt=n) "^nc_i "^n c_j is equal to 2^(2n-1)-((2n)!)/ (2(n !)^2)

Find the value of sumsum_(1leilejlt=n-1)(ij)^n c_i^n"" c_jdot

If a_(n) = sum_(r=0)^(n) (1)/(""^(n)C_(r)) , then the value of (sumsum)_(0leiltjlen) (i/(""^(n)C_(i))+j/(""^(n)C_(j)))

Find the sum sum_(i=0)^r.^(n_1)C_(r-i) .^(n_2)C_i .

Find the sum sum_(r=1)^n r^2(^n C_r)/(^n C_(r-1)) .