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A067605
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Least k such that the GCD( prime(k+1)-1, prime(k)-1 ) = 2n.
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3
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2, 6, 11, 24, 42, 121, 30, 319, 99, 1592, 344, 574, 3786, 4196, 650, 4619, 217, 1532, 11244, 5349, 8081, 3861, 12751, 18281, 9221, 5995, 22467, 16222, 43969, 35975, 192603, 108146, 52313, 218234, 15927, 132997, 42673, 78858, 103865, 84483
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Since all consecutive primes, p < q and p greater than 2, are odd, therefore the GCD( p-1, q-1 ) must be even.
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EXAMPLE
| n=4: a(4)=24=GCD[89-1,97-1]=GCD[p(24)-1,p(25)-1]=8=2n.
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MATHEMATICA
| a = Table[0, {100}]; p = 3; q = 5; Do[q = Prime[n + 1]; d = GCD[p - 1, q - 1]/2; If[d < 101 && a[[d]] == 0, a[[d]] = n]; b = c, {n, 2, 10^7}]; a
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CROSSREFS
| Cf. A063444, A084307, A058263.
Sequence in context: A103143 A005673 A084308 * A072986 A079047 A160966
Adjacent sequences: A067602 A067603 A067604 * A067606 A067607 A067608
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KEYWORD
| easy,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 31 2002
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