1,2

After 1, all terms are given by A153170 +2. [Bruno Berselli, Aug 21 2013]

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

8 is in the sequence since 3*8 - 4 = 20 is not prime.

Select[Range[230], ! PrimeQ[3 # - 4]&]

(MAGMA) [n: n in [1..120] | not IsPrime(3*n -4)];

Cf. A153170, A228121.

Sequence in context: A227405 A061408 A063287 * A134331 A276040 A090334

Adjacent sequences: A228355 A228356 A228357 * A228359 A228360 A228361

nonn,easy

Vincenzo Librandi, Aug 21 2013

approved