

A066388


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


12



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.
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 2*a(n)+1 divisible by 5, so only k=5m is possible.  M. F. Hasler, Nov 27 2010


LINKS



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



KEYWORD

nonn


AUTHOR



STATUS

approved



