A023511 Least odd prime divisor of prime(n) + 1, or 1 if prime(n) + 1 is a power of 2.

3, 1, 3, 1, 3, 7, 3, 5, 3, 3, 1, 19, 3, 11, 3, 3, 3, 31, 17, 3, 37, 5, 3, 3, 7, 3, 13, 3, 5, 3, 1, 3, 3, 5, 3, 19, 79, 41, 3, 3, 3, 7, 3, 97, 3, 5, 53, 7, 3, 5, 3, 3, 11, 3, 3, 3, 3, 17, 139, 3, 71, 3, 7, 3, 157, 3, 83, 13, 3, 5, 3, 3, 23, 11, 5, 3, 3, 199, 3, 5, 3, 211, 3, 7, 5, 3, 3

Offset

1,1

Comments

Note that a(n) = 1 for n= 2, 4, 11, 31, 1028, ... (A059305). - Michel Marcus, Oct 01 2013

Links

Table of n, a(n) for n=1..87.

Formula

a(n) = A078701(A008864(n)). - Michel Marcus, Jun 06 2019

Prog

(PARI) a(n) = my(p = prime(n) + 1, v = p/(2^valuation(p, 2))) ; if (v == 1, 1, factor(v)[1, 1]); \\ Michel Marcus, Oct 01 2013

Crossrefs

Cf. A008864, A078701.

Sequence in context: A046933 A185091 A332031 * A035628 A187562 A370719

Adjacent sequences: A023508 A023509 A023510 * A023512 A023513 A023514

Keyword

nonn

Author

Clark Kimberling

Status

approved