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 A194639 Indices of records in A194591 when it is restricted to odd indices. 13
 1, 5, 13, 47, 59, 109, 241, 335, 1109, 1373, 1447, 14893, 52267, 56543, 649603, 838441, 8840101, 16935761, 100604513, 118373279, 270704167, 1355477231 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Integers for which the smallest k in A194591 such that (2*n-1)*2^k - 1 or (2*n-1)*2^k + 1 is prime (A194638) increases. A194637 gives the record values of A194636. REFERENCES Wilfrid Keller, personal communication, 2010. LINKS Chris K. Caldwell, The List of Largest Known Primes, 1355477231 * 2^356981 + 1 Carlos Rivera, Problem 30 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, {}], {n, 10^5}]] (* Arkadiusz Wesolowski, Sep 04 2011 *) CROSSREFS Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194635, A194636, A194637, A194638. Cf. A064699, A076335, A180247, A217892. Cf. A217892 (indices of records of unrestricted A194591) Sequence in context: A099972 A060050 A217892 * A152925 A304964 A120790 Adjacent sequences:  A194636 A194637 A194638 * A194640 A194641 A194642 KEYWORD more,nonn AUTHOR Arkadiusz Wesolowski, Aug 31 2011 EXTENSIONS a(22) was found in 2002 by Wilfrid Keller. Definition corrected by Max Alekseyev and Farideh Firoozbakht, Oct 16 2014 STATUS approved

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Last modified August 20 05:25 EDT 2019. Contains 326139 sequences. (Running on oeis4.)