

A066388


Numbers n such that n and 2n are both between a pair of twin primes.


11



6, 30, 660, 810, 2130, 2550, 3330, 3390, 5850, 6270, 10530, 33180, 41610, 44130, 53550, 55440, 57330, 63840, 65100, 70380, 70980, 72270, 74100, 74760, 78780, 80670, 81930, 87540, 93240, 102300, 115470, 124770, 133980, 136950, 156420
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OFFSET

1,1


COMMENTS

Also terms of A014574 such that twice the term is also in A014574. Related to a problem of antidivisors.
A117499(a(n)) = 4.  Reinhard Zumkeller, Mar 23 2006
All a(n)>6 must be a multiple of 30: As for elements of A014574, we must have a(n) = 6k, and k=5m+/1 would lead to a(n)/+1 divisible by 5, while k=5m+/2 would lead to 2a(n)+/1 divisible by 5, so only k=5m is possible.  M. F. Hasler, Nov 27 2010


LINKS

Harry J. Smith, Table of n, a(n) for n=1,...,1000
Eric Weisstein's World of Mathematics, Bitwin Chain


EXAMPLE

For n=30, 29 and 31 are prime, as are 59 and 61.


MATHEMATICA

lst={}; Do[p1=Prime[n]; p2=Prime[n+1]; d=2; If[p2p1==d, w=p1+1; If[PrimeQ[2*w1]&&PrimeQ[2*w+1], AppendTo[lst, w]]], {n, 1, 10^4}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 07 2008 *)


PROG

(PARI) { n=0; forstep (m=2, 10^9, 2, if (isprime(m  1) && isprime(m + 1) && isprime(2*m  1) && isprime(2*m + 1), write("b066388.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 13 2010


CROSSREFS

Cf. A001359, A006512, A012574.
Sequence in context: A256545 A075591 A130075 * A222718 A200894 A202861
Adjacent sequences: A066385 A066386 A066387 * A066389 A066390 A066391


KEYWORD

nonn


AUTHOR

Jud McCranie, Dec 23 2001


STATUS

approved



