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.

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

Offset

0,4

Comments

2 is not a member.

Links

Table of n, a(n) for n=0..74.

Example

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

Mathematica

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 *)

Crossrefs

Cf. A073695, A073696.

Sequence in context: A304676 A316123 A146771 * A209414 A193636 A232968

Adjacent sequences: A073694 A073695 A073696 * A073698 A073699 A073700

Keyword

nonn

Author

Amarnath Murthy, Aug 12 2002

Extensions

More terms from Felice Russo, Oct 11 2002

Status

approved