The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.



(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A074259 Gaps between primes p such that 2p+1 is also prime, i.e., Sophie-Germain primes A005384. 2


%S 1,2,6,12,6,12,12,30,6,24,18,42,6,12,42,6,12,30,12,66,60,12,12,48,18,

%T 84,48,12,6,24,36,24,18,48,102,42,60,6,12,18,54,120,6,60,120,30,12,30,

%U 18,12,48

%N Gaps between primes p such that 2p+1 is also prime, i.e., Sophie-Germain primes A005384.

%C The first two consecutive identical gaps are 12, 12 between A005384(6..8) = (29, 41, 53).

%C The first three, four and five identical gaps in a row are equal to 30, 150 and 420, respectively, and occur after A005384(85) = 3299, A005384(29952) = 4866623, and A005384(32361449747) = 22081407211439. These were found by N. Fernandez and G. Resta, see link to discussion on the SeqFan mailing list. - _M. F. Hasler_, Sep 18 2016

%H M. F. Hasler, <a href="/A074259/b074259.txt">Table of n, a(n) for n = 1..7745</a>

%H Giovanni Resta, in reply to Harvey P. Dale and others, <a href="http://list.seqfan.eu/pipermail/seqfan/2016-September/016776.html">Re: Consecutive Sophie Germain primes with the same gap</a>, SeqFan mailing list, Sep. 2016. (Click "Previous message" to see <a href="http://list.seqfan.eu/pipermail/seqfan/2016-September/016771.html">Neil Fernandez' earlier results</a>.)

%t Select[Prime[Range[500]],PrimeQ[2#+1]&]//Differences (* _Harvey P. Dale_, Jul 15 2019 *)

%o (PARI) c=0; forprime(p=1+L=2,10^6,if(isprime(2*p+1),write("primegap.txt",c++," "p-L); L=p)) \\ Edited by _M. F. Hasler_, Sep 16 2016

%Y First differences of A005384.

%K nonn

%O 1,2

%A _Jon Perry_, Sep 20 2002

%E Edited (name, offset, more terms) by _M. F. Hasler_, Sep 16 2016

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 25 16:42 EST 2020. Contains 331245 sequences. (Running on oeis4.)