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%I #11 Apr 24 2019 04:40:52
%S 2,2,3,3,45,45,561330,9549960,42932385,13044904290,277344139215,
%T 277344139215,2045466215756535
%N a(n) = least k such that 2^i*k-1 is prime for 1<=i<=n.
%t k = 1; Do[If[n < 5, inc = 1, inc = 15];If[Mod[k, inc] > 0, k = k + inc - Mod[k, inc]];While[Nand @@ PrimeQ[Table[2^j, {j, n}]*k - 1], k += inc]; Print[k], {n, 1, 10}] (* _Ray Chandler_ *)
%Y Cf. A006254, A124485, A124493, A124494, A124017, A125113, A124514, A124515.
%Y Cf. A071576, A101994, A101320.
%K nonn,more
%O 1,1
%A _Artur Jasinski_, Nov 04 2006
%E Definition corrected and a(10) calculated by _Farideh Firoozbakht_, Nov 24 2006
%E a(11)-a(13) from _Giovanni Resta_, Apr 22 2019