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A176181
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Primes p(n) such that gcd(p(n)-1, p(n+1)-1) > gcd(p(n)+1, p(n+1)+1).
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2
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13, 31, 37, 61, 73, 89, 97, 109, 113, 151, 157, 181, 193, 199, 211, 229, 241, 271, 277, 313, 331, 349, 367, 373, 389, 397, 401, 421, 433, 449, 457, 523, 541, 571, 601, 607, 613, 619, 631, 661, 673, 691, 701, 727, 733, 751, 757, 761, 769, 811, 853, 877, 929
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OFFSET
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1,1
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COMMENTS
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Sequence does not contain any lesser of twin primes A001359. (Proof. If p(n+1) = p(n)+2, then gcd(p(n)-1, p(n+1)-1) = 2 = gcd(p(n)+1, p(n+1)+1), so p(n) is not a term.) - Jonathan Sondow, Feb 03 2012
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LINKS
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MATHEMATICA
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lst={}; Do[p0=Prime[n]; p1=Prime[n+1]; If[GCD[p0-1, p1-1] > GCD[p0+1, p1+1], AppendTo[lst, p0]], {n, 200}]; lst
Transpose[Select[Partition[Prime[Range[200]], 2, 1], GCD@@(#-1)>GCD@@(#+1)&]] [[1]] (* Harvey P. Dale, Sep 30 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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