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A029708 Numbers k such that k-2 and k+2 are consecutive primes. 6
9, 15, 21, 39, 45, 69, 81, 99, 105, 111, 129, 165, 195, 225, 231, 279, 309, 315, 351, 381, 399, 441, 459, 465, 489, 501, 615, 645, 675, 741, 759, 771, 825, 855, 861, 879, 885, 909, 939, 969, 1011, 1089, 1095, 1215, 1281, 1299, 1305, 1425, 1431 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are multiples of 3. Minimal first difference is 6. - Zak Seidov, May 15 2013

LINKS

Marius A. Burtea, Table of n, a(n) for n = 1..10548 (first 1000 terms from Zak Seidov )

Zak Seidov, Table of n, a(n)/3 for n = 1..1000

FORMULA

a(n) = (A029710(n) + A031505(n+1))/2 = A029710(n) + 2 = A031505(n+1) - 2.

MATHEMATICA

f[n_]:=PrimeQ[n-2]&&PrimeQ[n+2]; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 7, 8!, 2}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 09 2009 *)

Select[Range[9, 1432, 6], PrimeQ[#-2]&&PrimeQ[#+2]&] (* Zak Seidov, May 15 2013 - just for terms in DATA *)

PROG

(MAGMA) [k:k in [1..1500]| IsPrime(k-2) and NextPrime(k-2) eq k+2 ] // Marius A. Burtea, Jan 24 2019

CROSSREFS

Essentially the same as A087679.

Sequence in context: A063174 A072569 A072572 * A125215 A102739 A124622

Adjacent sequences:  A029705 A029706 A029707 * A029709 A029710 A029711

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified June 25 03:50 EDT 2019. Contains 324338 sequences. (Running on oeis4.)