A037039 Least k such that 4*n*k+1 is a prime.

1, 2, 1, 1, 2, 3, 1, 3, 1, 1, 2, 2, 1, 2, 1, 3, 2, 1, 3, 3, 4, 1, 3, 1, 1, 3, 1, 1, 2, 2, 3, 2, 3, 1, 2, 3, 1, 3, 1, 4, 5, 2, 1, 2, 1, 7, 5, 1, 1, 2, 2, 6, 5, 2, 3, 2, 1, 1, 3, 1, 3, 6, 3, 1, 2, 5, 1, 5, 1, 1, 2, 2, 1, 2, 2, 4, 2, 1, 1, 2, 4, 7, 3, 1, 3, 3, 1, 1, 3, 5, 3, 9, 1, 3, 2, 2, 1, 8, 1, 1, 2, 1, 3, 3, 1

Offset

1,2

Links

Table of n, a(n) for n=1..105.

Example

a(5)=2 because for n=5: 4*5*2+1=41 is a prime.

Prog

(PARI) a(n) = my(k = 0); while (! isprime(4*n*k+1), k++); k; \\ Michel Marcus, Sep 28 2013

Crossrefs

Cf. A016014.

Sequence in context: A097868 A025830 A083796 * A333856 A182972 A153452

Adjacent sequences: A037036 A037037 A037038 * A037040 A037041 A037042

Keyword

nonn

Author

Felice Russo

Extensions

More terms from Erich Friedman

Status

approved