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A176182
Primes p(n) such that gcd(p(n)-1, p(n+1)-1) < gcd(p(n)+1, p(n+1)+1).
0
7, 19, 23, 43, 47, 53, 67, 79, 83, 103, 127, 131, 139, 163, 167, 173, 223, 233, 251, 257, 263, 293, 307, 353, 359, 379, 383, 409, 439, 443, 463, 467, 479, 487, 491, 499, 503, 509, 557, 563, 587, 593, 643, 647, 653, 677, 683, 709, 719, 739, 743, 797, 823, 829
OFFSET
1,1
MATHEMATICA
lst={}; Do[p0=Prime[n]; p1=Prime[n+1]; If[GCD[p0-1, p1-1]<GCD[p0+1, p1+1], AppendTo[lst, p0]], {n, 6!}]; lst
Transpose[Select[Partition[Prime[Range[150]], 2, 1], GCD[First[#]-1, Last[#]-1]<GCD[First[#]+1, Last[#]+1]&]][[1]] (* Harvey P. Dale, Jul 06 2011 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved