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%I #9 Jul 16 2015 22:47:02
%S 1,2,5,7,8,10,11,13,14,16,17,18,20,21,22,23,24,25,26,27,28,29,32,33,
%T 34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,
%U 57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76
%N a(n) = smallest number > a(n-1) such that a(1)*a(2)*...*a(n) - 1 is nonprime.
%C The numbers 3, 4, 6, 8, 9, 12, 15, 19, 30, 31, 81, 152, 390, ... are not in the sequence.
%e 1-1 = 0, 1*2-1 = 1, 1*2*5-1 = 9, 1*2*5*7 - 1 = 69, etc. are nonprimes.
%t seq={1}; Do[n=Last[seq]+1; While[PrimeQ[n Times@@seq-1], n++]; AppendTo[ seq, n]; , {60}]; seq
%Y Cf. A051957, A233746.
%K nonn
%O 1,2
%A _Michel Lagneau_, Dec 15 2013