A111517 - OEIS

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A111517

Numbers n such that (7*n + 1)/2 is prime.

3, 15, 19, 31, 39, 43, 51, 55, 75, 79, 99, 111, 123, 139, 159, 163, 171, 175, 183, 195, 211, 231, 235, 259, 279, 283, 291, 295, 303, 315, 319, 339, 343, 351, 379, 411, 415, 423, 435, 451, 459, 463, 475

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

EXAMPLE

If n=279 then (7*n + 1)/2 = 977 (prime).

MATHEMATICA

Select[Range[500], PrimeQ[(7#+1)/2]&] (* Harvey P. Dale, May 07 2011 *)

PROG

(PARI) is(n)=isprime((7*n+1)/2) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS