O15-C905
> restart:
> i:=x->int((t^x-1)/(ln(t)),t=0..1);# Def_I=]-1,+infinity[

                                    1
                                   /   x
                                  |   t  - 1
                       i := x ->  |   ------ dt
                                  |   ln(t)
                                 /
                                   0

> i(x);

                               1
                              /   x
                             |   t  - 1
                             |   ------ dt
                             |   ln(t)
                            /
                              0

> plot(i(x),x=-.9..7);