A381793 Smallest k>1 such that 10*k^(5*2^n)+1 is prime.

6, 11, 649, 792, 1034, 12386, 21813, 87318, 35387, 207339, 67958

Offset: 0

Author

Jakub Buczak, Mar 07 2025

Keywords

• nonn
• base
• hard
• more

Examples

			a(0) = 6, because 10*6^(5*2^0)+1 equals 77761 which is prime.
		

Crossrefs

Cf. A020714, A089319.

Cf. A381815.

Programs

Python

from sympy import isprime
from itertools import count
def a(n): return next(k for k in count(2) if isprime(k**(5*(2**n)) * 10 + 1))

Extensions

a(7)-a(10) from Michael S. Branicky, Mar 07 2025