You are probably quite certain that the following numbers are irrational. But can you prove it?
a = 0.149162536496481...
b = 0.2357111317192329...
c = 0.1248163264128256...
Not quite sure, but if we say that this sequence exists of the
different primes concatenated as decimals, the sequence could not be
periodic, I guess. If this would indeed be the case, then the proposed
number is irrational.
This seems to be the case for a (the perfect squares concatenated) and
c (the powers of 2, where the last digit of a power is always even, but
the others become odd at some point, and the number of digits of a
power increases gradually -- this would make it impossible to make the
sequence periodic).