A370663 Numbers k such that (9^k + 9*k)/9 is prime.

1, 2, 4, 8, 10, 28, 1348, 1424, 12838

Offset

1,2

Comments

If it exists, a(10) > 50000.

Links

Table of n, a(n) for n=1..9.

Mathematica

Select[Range[1, 13000], PrimeQ[((9^#+9*#) / 9)]&] (* Vincenzo Librandi, Jul 04 2025 *)

Prog

(PARI) is(n) = ispseudoprime(9^(n-1)+n)
(Magma) [n: n in [1..130] |IsPrime ((9^n + 9*n) div 9)]; // Vincenzo Librandi, Jul 04 2025

Crossrefs

Cf. A221911, A226202.

Sequence in context: A387522 A056654 A365002 * A020950 A056386 A331027

Adjacent sequences: A370660 A370661 A370662 * A370664 A370665 A370666

Keyword

nonn,hard,more

Author

Hugo Pfoertner, Feb 27 2024

Status

approved