

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



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
(list;
graph;
refs;
listen;
history;
text;
internal format)



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



