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A087680 Numbers n such that n + 4 and n - 4 are both prime. 7
7, 9, 15, 27, 33, 57, 63, 75, 93, 105, 135, 153, 177, 195, 237, 267, 273, 363, 393, 405, 435, 453, 483, 495, 567, 573, 597, 603, 657, 687, 705, 723, 747, 765, 825, 915, 933, 987, 1017, 1035, 1065, 1113, 1167, 1197, 1227, 1233, 1287, 1293, 1323, 1377, 1443 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms > 7 (prime) are divisible by 3. Also note that n-4 and n+4 are not necessarily consecutive primes. First case when n-4 and n+4 are consecutive primes is for n=93 with n-4=89 and n+4=97. - Zak Seidov, Apr 22 2015

LINKS

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A023202(n) + 4. - Michel Marcus, Apr 22 2015

MAPLE

ZL:=[]:for p from 1 to 1444 do if (isprime(p) and isprime(p+8) ) then ZL:=[op(ZL), (p+(p+8))/2]; fi; od; print(ZL); # Zerinvary Lajos, Mar 07 2007

MATHEMATICA

f[n_]:=PrimeQ[n-4]&&PrimeQ[n+4]; lst={}; Do[If[f[n], AppendTo[lst, n]], {n, 3, 8!, 2}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 09 2009 *)

CROSSREFS

Cf. A023202, A014574, A087678-A087683, A087695-A087697, A088764.

Sequence in context: A111312 A158891 A213220 * A249333 A020691 A145830

Adjacent sequences:  A087677 A087678 A087679 * A087681 A087682 A087683

KEYWORD

easy,nonn

AUTHOR

Zak Seidov, Sep 27 2003

EXTENSIONS

More terms from Ray Chandler, Oct 26 2003

STATUS

approved

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Last modified September 25 23:23 EDT 2020. Contains 337346 sequences. (Running on oeis4.)