A065987 Numbers k such that the first k binary digits of Pi expressed in decimal forms a prime.

2, 23, 31, 35, 124, 323, 2787, 5717, 6506, 8980, 106817, 109773, 125244, 242974, 246353

Offset: 1

Author

Robert G. Wilson v, Dec 10 2001

Keywords

• base
• nonn
• more

Examples

			The first 23 binary digits of Pi (A004601) are 11001001000011111101101 = 6588397 in decimal, which is a prime.
		

Crossrefs

Cf. A004601, A117721 (the primes themselves), A333649.

Programs

Mathematica

Do[ If[ PrimeQ[ FromDigits[ First[ RealDigits[Pi, 2, n]], 2]], Print[n]], {n, 1, 7000} ]

Extensions

a(10) from Hans Havermann, Jul 23 2006

a(11) from Hans Havermann, Sep 06 2006

a(12)-a(13) from Michael S. Branicky, Sep 17 2024

a(14)-a(15) from Michael S. Branicky, Dec 19 2024