And some other simple questions

[Vitaliy A Repin]

Hello!

Several simple questions:

1) How can I compute the value $f(x)=Sum_{i=1}^{+\infty} some_func(i,x)$?
2) How can I compute the value $f(x)=\frac{d^n}{d\, x^n} g(x)$? 

Thanks &
Good-bye!
                                                                    WBR, Vitaly.
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Vitaly A. Repin, SpbSTU