A382393 Positive integers k such that 6*k - 1 is prime for k != 1 (mod 5) and (6*k - 1)/5 is prime for k == 1 (mod 5).

2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 22, 23, 25, 26, 28, 29, 30, 31, 32, 33, 36, 38, 39, 40, 42, 43, 44, 45, 47, 49, 51, 52, 53, 56, 58, 59, 60, 61, 64, 65, 66, 67, 70, 72, 74, 75, 77, 78, 80, 81, 82, 84, 85, 86, 87, 91, 93, 94, 95, 98, 99, 100

Offset: 1

Author

V. Barbera, Mar 23 2025

Keywords

• nonn

Comments

For all elements of this sequence, there are no pairs (x,y) of positive integers with x > 1 such that a(n)=6*x*y+x-y.

Crossrefs

Cf. A024898, A024899.

Programs

PARI

select(k->isprime((6*k-1)/(5-4*!(k==Mod(1,5)))), vector(100,i,i))