A087370 Numbers n such that 3n - 1 is a prime.

1, 2, 4, 6, 8, 10, 14, 16, 18, 20, 24, 28, 30, 34, 36, 38, 44, 46, 50, 56, 58, 60, 64, 66, 76, 78, 80, 84, 86, 88, 90, 94, 98, 104, 106, 116, 118, 120, 128, 130, 134, 140, 144, 148, 150, 154, 156, 160, 164, 168, 170, 174, 186, 188, 190, 196, 198, 200, 206, 214, 216

Offset

1,2

Comments

3*n - 1 is an Eisenstein prime. - Vincenzo Librandi, Aug 08 2010

For all elements of this sequence there are no pairs (x,y) of positive integers such that a(n) = 3*x*y - x + y. - Pedro Caceres, Jan 28 2021

References

M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988

Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta, UTET, CittaStudiEdizioni, Milano 1997

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Formula

a(n)= A024893(n) + 1 = A088879(n) + 2.

Prog

(Haskell)
a087370 n = a087370_list !! (n-1)
a087370_list = filter ((== 1) . a010051' . subtract 1 . (* 3)) [0..]
-- Reinhard Zumkeller, Jul 03 2015

Crossrefs

A003627 gives primes, A091177 gives prime index.

Cf. A010051, subsequence of A016789, A259645.

Sequence in context: A260391 A022292 A225241 * A364158 A138929 A334169

Adjacent sequences: A087367 A087368 A087369 * A087371 A087372 A087373

Keyword

easy,nonn

Author

Giovanni Teofilatto, Oct 21 2003

Extensions

Corrected and extended by Ray Chandler, Oct 22 2003

Status

approved