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

0,1

Links

Table of n, a(n) for n=0..10.

Example

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

Prog

(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))

Crossrefs

Cf. A020714, A089319.

Cf. A381815.

Sequence in context: A136980 A083834 A136978 * A145746 A024267 A028584

Adjacent sequences: A381790 A381791 A381792 * A381794 A381795 A381796

Keyword

nonn,base,hard,more

Author

Jakub Buczak, Mar 07 2025

Extensions

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

Status

approved