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Search: id:A087711
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| A087711 |
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a(n) = smallest number k such that both k-n and k+n are primes. |
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+0
4
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| 2, 4, 5, 8, 7, 8, 11, 10, 11, 14, 13, 18, 17, 16, 17, 22, 21, 20, 23, 22, 23, 26, 25, 30, 29, 28, 33, 32, 31, 32, 37, 36, 35, 38, 37, 38, 43, 42, 41, 44, 43, 48, 47, 46, 57, 52, 51, 50, 53, 52, 53, 56, 55, 56, 59, 58, 75, 70, 69, 72, 67, 66, 65, 68, 67, 72, 71, 70, 71, 80, 81, 78
(list; graph; listen)
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OFFSET
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0,1
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LINKS
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Zak Seidov, Table of n, a(n) for n=0..1000.
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EXAMPLE
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n=10: k=13 because 13-10 and 13+10 are both prime, and 13 is the smallest k such that k +/- 10 are both prime
4-1=3, prime, 4+1=5, prime; 5-2=3, 5+2=7; 8-3=5, 8+3=11; 9-4=5, 9+4=13, ...
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MATHEMATICA
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s = ""; k = 0; For[i = 3, i < 22^2, If[PrimeQ[i - k] && PrimeQ[i + k], s = s <> ToString[i] <> ", "; k++ ]; i++ ]; Print[s] - Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 03 2008
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PROGRAM
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(MAGMA) distance:=function(n); k:=n+2; while not IsPrime(k-n) or not IsPrime(k+n) do k:=k+1; end while; return k; end function; [ distance(n): n in [1..71] ]; /* Klaus Brockhaus, Apr 08 2007 */
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CROSSREFS
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Cf. A087695, A087696, A087697, A087678, A087679, A087680, A087681, A087682, A087683.
Cf. A082467. See A137169 for another version.
Adjacent sequences: A087708 A087709 A087710 this_sequence A087712 A087713 A087714
Sequence in context: A110991 A076990 A057168 this_sequence A123128 A057064 A088580
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KEYWORD
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easy,nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Sep 28 2003
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EXTENSIONS
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Entries checked by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Apr 08 2007
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