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

%I

%S 73,97,103,193,229,241,277,283,313,331,367,373,397,433,457,463,547,

%T 607,619,643,661,709,727,733,739,757,823,859,883,907,967,997,1021,

%U 1033,1069,1087,1093,1123,1129,1171,1237,1249,1303,1423,1447,1453,1483,1489,1543,1579,1597

%N a(n) = 1 + 3*A034782(n).

%C 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.

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

%o (PARI) a034693(n) = my(s=1); while(!isprime(s*n+1), s++); s;

%o isok(n) = a034693(n) == 3;

%o lista(nn) = {for (n=1, nn, if (isok(n), print1(3*n+1, ", ")););} \\ _Michel Marcus_, May 13 2018

%Y Cf. A034693, A034694, A034782.

%K nonn

%O 1,1

%A _Labos Elemer_

%E Corrected (wrong term 769 removed) and extended by _Michel Marcus_, May 13 2018

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Last modified January 18 13:38 EST 2019. Contains 319271 sequences. (Running on oeis4.)