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A195352
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Smallest prime p such that 2*n+1 = 2*p + q for some odd prime q.
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5
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2, 2, 2, 3, 2, 2, 3, 2, 2, 3, 2, 3, 7, 2, 2, 3, 5, 2, 3, 2, 2, 3, 2, 3, 7, 2, 3, 7, 2, 2, 3, 5, 2, 3, 2, 2, 3, 5, 2, 3, 2, 3, 19, 2, 3, 7, 5, 2, 3, 2, 2, 3, 2, 2, 3, 2, 3, 7, 5, 11, 7, 11, 2, 3, 2, 3, 13, 2, 2, 3, 5, 5, 7, 2, 2, 3, 5, 2, 3, 7, 2, 3, 2, 3, 13
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OFFSET
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3,1
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COMMENTS
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Related to Lemoine's conjecture, which states that all odd integers > 5 can be represented as 2*p+q, p, q primes.
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REFERENCES
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LINKS
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EXAMPLE
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a(3)=2 because 2*3+1=7=2*2+3; a(4)=2: 2*3+1=9=2*2+5; a(5)=2: 11=2*2+7; a(6)=3: 13=2*3+7.
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MATHEMATICA
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spp[n_]:=Module[{p=2}, While[CompositeQ[(2n+1)-2p], p=NextPrime[p]]; p]; Array[ spp, 90, 3] (* Harvey P. Dale, Jun 02 2022 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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