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A120876
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(Product of twin primes - 1)/2.
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5
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7, 17, 71, 161, 449, 881, 1799, 2591, 5201, 5831, 9521, 11249, 16199, 18431, 19601, 25991, 28799, 36449, 39761, 48671, 60551, 88199, 93311, 106721, 136241, 162449, 179999, 190961, 206081, 217799, 328049, 337841, 342791, 368081, 388961, 520199, 532511, 551249, 563921
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OFFSET
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1,1
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COMMENTS
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This sequence is a subsequence of A102770.
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LINKS
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FORMULA
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a(n) = 18*A002822(n-1)^2-1, for n>1.
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MATHEMATICA
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(Times@@#-1)/2&/@Select[Partition[Prime[Range[200]], 2, 1], Last[#]- First[#]== 2&] (* Harvey P. Dale, Jun 26 2011 *)
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PROG
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(PARI) for(n=1, 200, if(prime(n+1)-prime(n)==2, print1((prime(n)*prime(n+1)-1)/2", "))) \\ Altug Alkan, Oct 23 2015
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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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