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 A194637 Record values in A194636. 12
 0, 1, 2, 4, 5, 6, 11, 18, 20, 28, 70, 106, 150, 726, 2906, 7431, 14073, 22394, 41422, 82587, 85461, 356981 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The index sequence is 1, 3, 7, 24, 30, 55, 121, 168, 555, 687, 724, 7447, 26134, 28272, 324802, 419221, 4420051, 8467881, 50302257, 59186640, 135352084, 677738616, ... given by formula (A194639(n)+1)/2. REFERENCES Wilfrid Keller, personal communication, 2010. LINKS Chris K. Caldwell, The List of Largest Known Primes, 1355477231 * 2^356981 + 1 Carlos Rivera, Problem 30 FORMULA a(n) = A194591(A194639(n)) = A194636((A194639(n)+1)/2). EXAMPLE A194636(55) = 6 since A194636(121) = 11 is the next record value. MATHEMATICA l = -1; Flatten[Table[n = 2*n - 1; k = 0; While[! PrimeQ[n*2^k - 1] && ! PrimeQ[n*2^k + 1], k++]; If[k > l, l = k, {}], {n, 10^5}]] (* Arkadiusz Wesolowski, Sep 04 2011 *) CROSSREFS Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194635, A194636, A194638, A194639. Cf. A103963, A103964, A076335, A180247. Sequence in context: A101951 A171166 A194607 * A194600 A255543 A256458 Adjacent sequences:  A194634 A194635 A194636 * A194638 A194639 A194640 KEYWORD more,nonn AUTHOR Arkadiusz Wesolowski, Aug 31 2011 EXTENSIONS a(22) was found in 2002 by Wilfrid Keller. STATUS approved

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Last modified February 26 11:49 EST 2020. Contains 332279 sequences. (Running on oeis4.)