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%I #17 Oct 19 2017 03:14:03
%S 1,1,1,165,5415,12705,256410,256410,6480303060,217245863835,
%T 946622690475,35511547806735,439116128090640,5714676453270219435
%N a(n) = least k such that 2ik + 1 is prime for all 1 <= i <= n.
%t k = 1; Do[ While[p = Table[2*i*k + 1, {i, 1, n}]; Union[ PrimeQ[p]] != {True}, k++ ]; Print[k], {n, 1, 15}] (* _Robert G. Wilson v_ *)
%o (PARI) for(n=1,6,s=1; while(sum(i=1,n,isprime(2*s*i+1))<n,s++); print1(s,","))
%Y Cf. A088250, A124516, A124522, A124522, A063983.
%Y Cf. A005097, A123998, A124408-A124411.
%K more,nonn
%O 1,4
%A _Benoit Cloitre_, May 31 2002
%E Extended by _Robert G. Wilson v_, Jun 06 2002
%E a(9) from _Ryan Propper_, Jun 20 2005
%E a(10)-a(13) from _Don Reble_, Nov 05 2006
%E a(14) from _Giovanni Resta_, Apr 01 2017
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