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A175666 Sum of Sophie Germain prime p and corresponding safe prime q=2p+1. 1
7, 10, 16, 34, 70, 88, 124, 160, 250, 268, 340, 394, 520, 538, 574, 700, 718, 754, 844, 880, 1078, 1258, 1294, 1330, 1474, 1528, 1780, 1924, 1960, 1978, 2050, 2158, 2230, 2284, 2428, 2734, 2860, 3040, 3058, 3094, 3148, 3310, 3670, 3688, 3868, 4228, 4318 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For n > 1, numbers of the form 6k-2 such that Omega( (2k-1)(4k-1) ) = 2. - Wesley Ivan Hurt, Jun 28 2013

First semiprimes: 10,34,394,538,718,1294,2734. - Zak Seidov, Sep 07 2016

LINKS

Table of n, a(n) for n=1..47.

FORMULA

a(n) = A005384(n)+A005385(n) = 3*A005384(n)+1 = (3*A005385(n)-1)/2.

PROG

(PARI) is(n)=n%3==1 && isprime(n\3) && isprime((2*n+1)/3) \\ Charles R Greathouse IV, Jun 28 2013

CROSSREFS

Cf. A005384, A005385.

Sequence in context: A033817 A286873 A218128 * A299997 A299987 A192273

Adjacent sequences:  A175663 A175664 A175665 * A175667 A175668 A175669

KEYWORD

nonn

AUTHOR

Zak Seidov, Aug 05 2010

STATUS

approved

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Last modified July 10 23:30 EDT 2020. Contains 335600 sequences. (Running on oeis4.)