[forget it ]
You want a function from onto
Note there is no qualification on integrable. Presumably the OP is interested in something like Riemann integrability rather than Lesbegue integrability. Which is just as well as all the functions presented are Lesbegue integrable (since is countable and hence of measure zero).
RonL
This problem just does not make any sense. The way the Riemann integral is defined we use the condition that is bounded on which certainly makes it impossible for it to be onto . Unless you have a different understanding of integration, maybe you are thinking about improper integration?