[Dr Sardonicus]

Originally Posted by LaurV

See this thread.

Ah, yes, the "primes in π" thread.

Since a(n) is standard notation for OEIS sequences, I had tried such sequences related to digits of pi.

The Wolfram Mathworld page on Pi Digits lists URLs of the the OEIS sequences a(n) for first occurrence of n consecutive decimal digits d, d = 0 to 9, in the decimal expansion of pi.

The largest value of n in any of these, however, is n = 14, for d = 0, 5, 7, and 9. These are in the first 1.21 x 10¹³ digits.

I suppose there might be a small chance of finding a(15) in one of these sequences among the first 6.28 x 10¹³ digits.