A392300 Numbers k such that 25*2^k + 9 is prime.

1, 2, 4, 5, 6, 7, 9, 10, 12, 14, 17, 28, 30, 34, 46, 50, 76, 82, 84, 108, 155, 179, 185, 186, 190, 210, 249, 287, 338, 505, 530, 537, 1534, 1589, 1627, 1737, 3507, 3628, 4565, 4999, 6317, 6990, 8739, 8958, 10746, 14414, 14749, 18041, 22906, 24610, 25338, 25726

Offset

1,2

Links

Michael S. Branicky, Table of n, a(n) for n = 1..59 (all terms <= 100000)

Example

6 is in this sequence because 25*2^6 + 9 = 1609 is prime.
Initial terms and associated primes:
  a(1) = 1, 59;
  a(2) = 2, 109;
  a(3) = 4, 409;
  a(4) = 5, 809;
  a(5) = 6, 1609;
  a(6) = 7, 3209, etc.

Prog

(PARI) is(k) = ispseudoprime(25*2^k + 9)

Crossrefs

Cf. A166560.

Sequence in context: A218544 A286045 A127032 * A350396 A255165 A047316

Adjacent sequences: A392297 A392298 A392299 * A392301 A392302 A392303

Keyword

nonn

Author

Zhicheng Wei, Feb 05 2026

Status

approved