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%I #9 Apr 01 2017 17:26:44
%S 3,4,4,6,6,2100,2100,105828450,3533468190,240544635660,7392639784530,
%T 1896344521244250,5389539504929580,68086992545221650
%N a(n) is the smallest number m such that (2k-1)m - 1 is prime for all 0 < k < n+1.
%t a[n_] := Block[{k=1}, While[! AllTrue[k Range[1, 2 n - 1, 2] - 1, PrimeQ], k++]; k]; Array[a, 7] (* _Giovanni Resta_, Apr 01 2017 *)
%Y Cf. A071576, A164325.
%K more,nonn
%O 1,1
%A _Farideh Firoozbakht_, Sep 16 2009
%E a(10) from _Zak Seidov_, Sep 21 2009
%E a(11)-a(14) from _Giovanni Resta_, Mar 31 2017
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