#TI-BASIC, 16 bytes
TI-BASIC, 16 bytes
Basically tests if the input N
(1-indexed) is a triangular number. This is the same as returning the N
th digit of 0.1010010001…, which is proven to be transcendental. The sequence of digits is OEIS A010054.
Input N
int(√(2N
2N=Ans(Ans+1