A365958 Least k such that 8*n*k+1 is a prime.

2, 1, 3, 3, 1, 2, 2, 3, 1, 3, 1, 1, 3, 1, 2, 2, 1, 3, 3, 4, 2, 2, 7, 1, 2, 6, 2, 2, 1, 1, 6, 1, 5, 5, 1, 2, 2, 4, 1, 2, 7, 1, 3, 1, 5, 9, 3, 2, 8, 1, 1, 3, 4, 1, 2, 1, 1, 2, 4, 7, 2, 3, 2, 15, 1, 4, 3, 10, 3, 5, 1, 1, 3, 1, 1, 2, 1, 2, 6, 1, 2, 12, 3, 1, 2

Offset: 1

Author

Robert Price, Dec 17 2023

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A016014, A005123.

A070852 lists the corresponding primes.

Programs

Mathematica

A365958 = {};
Do[k=1; While[!PrimeQ[8 n k+1], k++]; AppendTo[A365958 ,k], {n,85}];
A365958

PARI

a(n) = my(k=1); while (!isprime(8*n*k+1), k++); k; \\ Michel Marcus, Dec 17 2023