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A071407
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a(n) is the smallest multiplier of p[n], n-th prime, such that both -1+a(n)p(n) and 1+a(n)p(n) are primes.
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1
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2, 2, 6, 6, 18, 24, 6, 12, 6, 12, 42, 54, 30, 24, 6, 120, 18, 258, 24, 18, 84, 132, 54, 48, 114, 42, 6, 6, 48, 24, 144, 30, 6, 12, 12, 78, 24, 36, 30, 54, 132, 18, 90, 36, 66, 18, 42, 30, 120, 30, 36, 42, 18, 18, 54, 84, 60, 12, 210, 12, 6, 60, 150, 102, 6, 210, 30, 24, 6
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| n=4:p(4)=7, a(4)=6, a(6)p(6)=42 and {41,43} are primes.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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MATHEMATICA
| Table[fl=1; Do[s=(Prime[j])*k; If[PrimeQ[s-1]&&PrimeQ[s+1]&&Equal[fl, 1], Print[{j, k}]; fl=0], {k, 1, 2*j^2}], {j, 0, 100}]
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CROSSREFS
| Cf. A071256, A071404-A071406, A060256, A060210.
Sequence in context: A011260 A117855 A086442 * A109859 A128057 A128014
Adjacent sequences: A071404 A071405 A071406 * A071408 A071409 A071410
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), May 24 2002
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