1.

If P_r stands for "^rP_r, then the value of 1+1.P_1 +2.P_2+3.P_3+....+n.P_n is :

Answer»

`(n-1)!/2`
`(n+1)!/2`
`2(n-1)!`
`(n+1)!`

ANSWER :D


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