A164326 a(n) is the smallest number m such that (2k-1)m - 1 is prime for all 0 < k < n+1.
3, 4, 4, 6, 6, 2100, 2100, 105828450, 3533468190, 240544635660, 7392639784530, 1896344521244250, 5389539504929580, 68086992545221650
Offset: 1
Programs
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Mathematica
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 *)
Extensions
a(10) from Zak Seidov, Sep 21 2009
a(11)-a(14) from Giovanni Resta, Mar 31 2017