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A163634
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a(n) = (p*(p+4)+1)/2 where (p,p+4) are the n-th cousin prime pair.
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1
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11, 39, 111, 219, 759, 1011, 2379, 3279, 4899, 5511, 6159, 8319, 13611, 19011, 25311, 26679, 38919, 47739, 49611, 61599, 72579, 79599, 97239, 105339, 108111, 119559, 125499, 189111, 208011, 227811, 274539, 288039, 297219, 340311, 365511, 370659
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(1) = (3* 7 + 1)/2 = 11;
a(2) = (7*11 + 1)/2 = 39;
a(3) = (13*17 + 1)/2 = 111.
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MATHEMATICA
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(fQ[n_]:=Block[{fi=FactorInteger@n}, Last@#&/@fi=={1, 1}&&Differences[First@#&/@fi]=={4}]; Select[Range@8000000, fQ] + 1)/2 (* Vincenzo Librandi Jan 02 2018 *)
Join[{11}, (1+Times@@#)/2&/@Select[Partition[Prime[Range[250]], 2, 1], #[[2]]- #[[1]]==4&]] (* Harvey P. Dale, Apr 04 2022 *)
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PROG
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(Magma) [(p*(p+4)+1)/2: p in PrimesUpTo(1000)| IsPrime(p+4)]; // Vincenzo Librandi, May 17 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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