This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A194639 #35 Apr 03 2023 10:36:12
%S A194639 1,5,13,47,59,109,241,335,1109,1373,1447,14893,52267,56543,649603,
%T A194639 838441,8840101,16935761,100604513,118373279,270704167,1355477231
%N A194639 Indices of records in A194591 when it is restricted to odd indices.
%C A194639 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.
%C A194639 A194637 gives the record values of A194636.
%D A194639 Wilfrid Keller, personal communication, 2010.
%H A194639 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 A194639 Carlos Rivera, <a href="http://www.primepuzzles.net/problems/prob_030.htm">Problem 30</a>
%t A194639 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 *)
%Y A194639 Cf. A194591, A194600, A194603, A194606, A194607, A194608, A194635, A194636, A194637, A194638.
%Y A194639 Cf. A064699, A076335, A180247, A217892.
%Y A194639 Cf. A217892 (indices of records of unrestricted A194591)
%K A194639 more,nonn
%O A194639 1,2
%A A194639 _Arkadiusz Wesolowski_, Aug 31 2011
%E A194639 a(22) was found in 2002 by Wilfrid Keller.
%E A194639 Definition corrected by _Max Alekseyev_ and _Farideh Firoozbakht_, Oct 16 2014