Please check where am i mistaking?
why r u writing an in formula? , it is an,
in part (e), at last step , u forgot to write n! in denominator.
in part (f), for 1/(1+x), an will be (-1)n
The question is same as http://gateoverflow.in/133771/discrete-maths-exponent-generating-function .So i am removing n! in the end to ge only an.
You mentioned t is an ,which t are you talking about?
My answer for e:) is not matching. It is given ( (-2)^n )+n! . Why is this + before n! ?.
X->YZ , Y->XZ , ...