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A120382 Even numbers n such that 3*n-1 and 3*n+1 are not prime. 0
40, 48, 62, 68, 72, 82, 96, 100, 108, 114, 138, 142, 158, 172, 176, 178, 184, 194, 208, 212, 222, 232, 238, 260, 264, 268, 272, 278, 282, 290, 298, 300, 308, 320, 334, 342, 348, 352, 358, 360, 378, 380, 382, 386, 392, 402, 414, 418, 422, 424, 438, 444, 446, 448, 450 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

FORMULA

a(n) = 2*A060461(n). - Michel Marcus, Sep 15 2019

PROG

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

CROSSREFS

Cf. A060461.

Sequence in context: A197734 A114839 A179435 * A290017 A062909 A167327

Adjacent sequences:  A120379 A120380 A120381 * A120383 A120384 A120385

KEYWORD

easy,nonn

AUTHOR

Pierre CAMI, Jun 29 2006

EXTENSIONS

More terms from Michel Marcus, Sep 15 2019

STATUS

approved

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Last modified March 31 16:44 EDT 2020. Contains 333151 sequences. (Running on oeis4.)