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A087680
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Numbers n such that n + 4 and n - 4 are both prime.
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7
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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
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OFFSET
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1,1
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COMMENTS
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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
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LINKS
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FORMULA
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MAPLE
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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
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MATHEMATICA
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Select[Prime[Range[250]], PrimeQ[#+8]&]+4 (* Harvey P. Dale, May 21 2023 *)
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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