Let's say that we are trying to catch the attention of other potentially intelligent species. This signal would be used to attract the attention of other intelligent species. If another species (of any possible number system, shape, technology...) were to intercept this signal, they could assume that it was from another intelligent species. For example, we could transmit:
, which is pi in binary, both of which are concepts likely to have been developed in another species.
What would be a (semi-)universally understood signal to transmit to show to other species that we are intelligent?