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A120382 Even numbers n such that 3*n-1 and 3*n+1 are not prime. 0

%I #7 Sep 16 2019 08:53:41

%S 40,48,62,68,72,82,96,100,108,114,138,142,158,172,176,178,184,194,208,

%T 212,222,232,238,260,264,268,272,278,282,290,298,300,308,320,334,342,

%U 348,352,358,360,378,380,382,386,392,402,414,418,422,424,438,444,446,448,450

%N Even numbers n such that 3*n-1 and 3*n+1 are not prime.

%F a(n) = 2*A060461(n). - _Michel Marcus_, Sep 15 2019

%o (PARI) isok(n) = !(n%2) && !isprime(3*n-1) && !isprime(3*n+1); \\ _Michel Marcus_, Sep 15 2019

%Y Cf. A060461.

%K easy,nonn

%O 1,1

%A _Pierre CAMI_, Jun 29 2006

%E More terms from _Michel Marcus_, Sep 15 2019

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Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)