1,2

Table of n, a(n) for n=1..51.

a(1)=1 because 1 and 3 are both in A002822.

(PARI) isokp(n) = isprime(6*n-1) && isprime(6*n+1);

isok(k) = isokp(k) && isokp(k+2); \\ Michel Marcus, May 15 2020

Cf. A002822, A173233.

Sequence in context: A102772 A018005 A080522 * A132332 A209001 A240619

Adjacent sequences: A173229 A173230 A173231 * A173233 A173234 A173235

nonn

Juri-Stepan Gerasimov, Feb 13 2010

Definition corrected, and sequence corrected (1158 inserted) by R. J. Mathar, May 02 2010

More terms from Jinyuan Wang, May 15 2020

approved