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A243158
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Smallest k>=0 such that prime(n)*prime(n+k) + 2 is prime.
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3
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0, 1, 1, 3, 1, 5, 1, 3, 4, 4, 3, 5, 2, 6, 13, 5, 6, 1, 9, 28, 8, 2, 10, 8, 5, 8, 3, 3, 31, 2, 2, 9, 6, 1, 3, 6, 2, 5, 4, 1, 10, 3, 7, 3, 6, 7, 4, 4, 1, 14, 1, 1, 4, 4, 18, 1, 8, 1, 3, 10, 3, 1, 6, 1, 7, 2, 26, 19, 6, 2, 8, 30, 23, 6, 19, 5, 1, 1, 12, 1, 7
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OFFSET
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2,4
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COMMENTS
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A dual sequence to A243154. The sequence contains a unique zero term. Indeed, every prime p>3 has the form 3*k +/- 1. So, p^2 + 2 == 0 (mod 3).
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LINKS
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MATHEMATICA
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skp[n_]:=Module[{c=Prime[n], k=0}, While[!PrimeQ[c*Prime[n+k]+2], k++]; k]; Array[ skp, 90, 2] (* Harvey P. Dale, May 08 2021 *)
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PROG
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(PARI) vector(200, n, k=0; while(!isprime(prime(n+1)*prime(n+1+k)+2), k++); k) \\ Colin Barker, May 31 2014
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CROSSREFS
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KEYWORD
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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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