The value of n∑r=1r nCr nCr−1 is
If the nth term of the sequence is given by (n2−1)(n+1) , then the sum of first n terms of the sequence is given by
If (1+x)n=C0+C1x+C2x2+.......+Cnxn, then C1C0+2C2C1+3C3C2+........+nCnCn−1=