A034848 a(n) = 1 + 3*A034782(n).

73, 97, 103, 193, 229, 241, 277, 283, 313, 331, 367, 373, 397, 433, 457, 463, 547, 607, 619, 643, 661, 709, 727, 733, 739, 757, 823, 859, 883, 907, 967, 997, 1021, 1033, 1069, 1087, 1093, 1123, 1129, 1171, 1237, 1249, 1303, 1423, 1447, 1453, 1483, 1489, 1543, 1579, 1597

Offset: 1

Author

Labos Elemer

Keywords

• nonn

Comments

a(n) = P(n,3) = 1 + 3*K(n,3) = 1 + 3*A034782(n). P(n,3) are special primes of the form 3k+1. The relevant values of k are given by A034782.

Note that, e.g., 13, 19, 31, 5, 13 are not in this sequence.

Crossrefs

Cf. A034693, A034694, A034782.

Programs

PARI

a034693(n) = my(s=1); while(!isprime(s*n+1), s++); s;
isok(n) = a034693(n) == 3;
lista(nn) = {for (n=1, nn, if (isok(n), print1(3*n+1, ", ")););} \\ Michel Marcus, May 13 2018

Extensions

Corrected (wrong term 769 removed) and extended by Michel Marcus, May 13 2018