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A092527
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If M(n) is the n-th Mersenne prime, then a(n) is the smallest positive integer such that 2*a(n)*M(n)*M(n+1)-1 is prime.
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1
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1, 1, 1, 12, 1, 25, 3, 13, 7, 153, 43, 423, 52, 916, 136, 1111, 1270, 442, 2737, 975
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| a(4) = 12: 2(12)(2^7-1)(2^13-1)-1 = 24(127)(8191)-1 = 24966167, which is prime.
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MATHEMATICA
| p = { (* the list of Mersenne exponents in A000043 *) }; f[n_] := Block[{k = 1, q = 2^p[[n]] - 1, r = 2^p[[n + 1]] - 1}, While[ !PrimeQ[2k*q*r - 1], k++ ]; k]; Do[ Print[ f[n]], {n, 25}] (from Robert G. Wilson v Apr 10 2004)
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CROSSREFS
| Sequence in context: A040155 A036185 A013619 * A085840 A075072 A038327
Adjacent sequences: A092524 A092525 A092526 * A092528 A092529 A092530
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KEYWORD
| nonn
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AUTHOR
| Ray G. Opao (1260(AT)email.com), Apr 08 2004
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EXTENSIONS
| a(21)>4200 - Robert G. Wilson v.
a(21)>12000, a(22)=6669, a(23)>10000, a(24)=5970. - Ray G. Opao (1260(AT)email.com), Apr 15 2004
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