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%I #17 Feb 24 2024 20:15:38
%S 0,4,14,8,11,22420,78,17,24,20,25,24,63,30,42,69,128,50,119,204,2816,
%T 76,52,288,64,66,184,153,67,268,78,210,438,295,96,74,136,128,2900,
%U 1898,130,92,381,106,18626,97,98,1650,747,109,214,113,312,354,1702,560,2798,123,171,554,11210,834,208,990,9271
%N Least number k > (2n-1) such that (2n-1)^k - 2 is prime, or 0 if no such number exists.
%C a(66) > 40000. - _Robert Price_, Mar 02 2015
%H Henri Lifchitz & Renaud Lifchitz: <a href="http://www.primenumbers.net/prptop/prptop.php">PRP Records. Probable Primes Top 10000</a>.
%F A128472(n) = (2n-1)^a(n) - 2 for n > 1.
%Y Cf. A128472 (smallest prime of the form (2n-1)^k - 2 for k > (2n-1), or 0 if no such number exists).
%Y Cf. A084714 (smallest prime of the form (2n-1)^k - 2, or 0 if no such number exists.
%Y Cf. A014224, A109080, A090669, A128455, A128457, A128458, A128459, A128460, A128461.
%Y Cf. A133858, A133982.
%K nonn
%O 1,2
%A _Alexander Adamchuk_, Oct 01 2007
%E a(6) = 22420 was found by _Rick L. Shepherd_, Sep 29 2009
%E a(21)-a(44) from _Max Alekseyev_, Oct 04 2007
%E a(45)-a(65) from _Robert Price_, Mar 02 2015
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