

A230515


Numbers n such that n*(n+1)1 is a Sophie Germain prime.


2



2, 3, 5, 6, 9, 11, 15, 20, 38, 39, 45, 48, 50, 54, 59, 93, 126, 131, 144, 149, 153, 174, 176, 218, 231, 236, 240, 246, 248, 263, 285, 306, 309, 330, 335, 374, 380, 395, 396, 401, 419, 423, 449, 455, 468, 471, 474, 495, 501, 506, 549, 551, 560, 588
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OFFSET

1,1


COMMENTS

This sequence is interesting because of the conjecture associated with A230514.


LINKS

ZhiWei Sun, Table of n, a(n) for n = 1..10000


EXAMPLE

a(1) = 2 since 2*3  1 = 5 is a Sophie Germain prime.
a(2) = 3 since 3*4  1 = 11 is a Sophie Germain prime.
a(3) = 5 since 5*6  1 = 29 is a Sophie Germain prime but 4*5  1 = 19 is not.


MATHEMATICA

q[n_]:=PrimeQ[n(n+1)1]&&PrimeQ[2n(n+1)1]
m=0
Do[If[q[n], m=m+1; Print[m, " ", n]], {n, 1, 506}]


PROG

(MAGMA) [n: n in [1..600]  IsPrime(n*(n+1)1) and IsPrime(2*n*(n+1)1)]; // Bruno Berselli, Oct 22 2013


CROSSREFS

Cf. A000040, A005384, A230514.
Subsequence of A045546.
Sequence in context: A008772 A008771 A008770 * A030068 A239958 A008769
Adjacent sequences: A230512 A230513 A230514 * A230516 A230517 A230518


KEYWORD

nonn


AUTHOR

ZhiWei Sun, Oct 21 2013


STATUS

approved



