%I #14 Jan 28 2018 13:09:01
%S 1,2,2,6,6,6,6,192660,437286240,37202202450,148684126500,
%T 2258581791060,161082438032880
%N Smallest k such that k*prime(i)+1 is prime for i = 1 to n.
%C For n > 7, a(n) == 0 mod 30.
%C Conjecture: log a(n) ~ C n log n. - _Thomas Ordowski_, Nov 20 2017
%e a(4) = a(5) = a(6) = a(7) = 6 as 2*6+1 = 13, 3*6+1 = 19, 5*6+1 = 31, 7*6+1 = 43, 11*6+1 = 67, 13*6+1 = 79, 17*6+1 = 103 are all primes.
%t k = 2; Do[ While[ Union[ PrimeQ[ Table[ k*Prime[i] + 1, {i, 1, n}]]] != {True}, k+=2]; Print[k], {n, 2, 8}]
%Y Cf. A084701.
%K more,nonn
%O 1,2
%A _Amarnath Murthy_, Jun 08 2003
%E Edited and extended by _Robert G. Wilson v_ and _Don Reble_, Jun 15 2003
%E Terms 11, 12 and 13 found by Phil Carmody using his GenSv generic siever, Mar 08 2004