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Record values in A194636.
12

%I #18 Apr 03 2023 10:36:12

%S 0,1,2,4,5,6,11,18,20,28,70,106,150,726,2906,7431,14073,22394,41422,

%T 82587,85461,356981

%N Record values in A194636.

%C 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.

%D Wilfrid Keller, personal communication, 2010.

%H Chris K. Caldwell, The List of Largest Known Primes, <a href="https://t5k.org/primes/page.php?id=107">1355477231 * 2^356981 + 1</a>

%H Carlos Rivera, <a href="http://www.primepuzzles.net/problems/prob_030.htm">Problem 30</a>

%F a(n) = A194591(A194639(n)) = A194636((A194639(n)+1)/2).

%e A194636(55) = 6 since A194636(121) = 11 is the next record value.

%t 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 *)

%Y Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194635, A194636, A194638, A194639.

%Y Cf. A103963, A103964, A076335, A180247.

%K more,nonn

%O 1,3

%A _Arkadiusz Wesolowski_, Aug 31 2011

%E a(22) was found in 2002 by Wilfrid Keller.