Consider the given function:
c1c0+2c2c1+3c3c2+4c4c3+......+ncncn−1
=n1+2n(n−1)2!.1n+3n(n−1)(n−2)3!.1n(n−1)2!+......+n.1n
=n+(n−1)+(n−2)+......1
=1+2+3+......+n
=n(n+1)2
Hence this is the answer.