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A073697 Group the even numbers so that the product of the terms in each group + 1 is a prime: (2), (4), (6), (8, 10, 12, 14), (16), (18), ... Sequence gives number of terms in each group. 2

%I

%S 1,1,1,4,1,1,7,8,3,6,52,1,27,1,7,8,4,1,1,12,82,1,1,11,1,5,1,5,3,73,7,

%T 1,42,22,8,1,20,8,1,1,5,6,1,12,3,30,5,1,5,1,14,1,25,1,35,4,75,7,45,12,

%U 3,9,10,17,31,1,7,3,3,4,1,3,16,9,3

%N Group the even numbers so that the product of the terms in each group + 1 is a prime: (2), (4), (6), (8, 10, 12, 14), (16), (18), ... Sequence gives number of terms in each group.

%C 2 is not a member.

%e 2; 4; 6; 8, 10, 12, 14; 16; 18; ...

%t t = {}; s = 1; c = 0; Do[s = s*i; c += 1; If[PrimeQ[s + 1], AppendTo[t, c]; s = 1; c = 0], {i, 2, 1700, 2}]; t (* _Jayanta Basu_, Jul 07 2013 *)

%Y Cf. A073695, A073696.

%K nonn

%O 0,4

%A _Amarnath Murthy_, Aug 12 2002

%E More terms from _Felice Russo_, Oct 11 2002

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Last modified August 18 00:56 EDT 2019. Contains 326059 sequences. (Running on oeis4.)