A144946 Least a(n) such that p(n)#*(p(n)#+a(n))-1 is prime with p(i)#=i-th primorial.

1, 1, 1, 2, 1, 1, 8, 21, 5, 4, 4, 4, 32, 4, 16, 7, 9, 1, 14, 5, 32, 22, 35, 6, 21, 11, 22, 3, 72, 48, 20, 1, 8, 1, 36, 30, 32, 6, 26, 14, 2, 22, 32, 6, 48, 37, 2, 58, 1, 74

Offset

1,4

Comments

As n increases sum(a(i)) for i=1 to n tends to e^gamma/2*n*(n+1)/2, notice that n*(n+1)/2 is triangular number. [From Pierre CAMI, Oct 16 2008]

Links

Pierre CAMI, Table of n, a(n) for n = 1..500

Example

2*(2+1)-1=5 prime so a(1)=1 6*(6+1)-1=41 prime so a(2)=1 30*(31)-1=929 prime so a(3)=1.

Crossrefs

Cf. A144947

Sequence in context: A225848 A165889 A087127 * A332717 A260374 A157109

Adjacent sequences: A144943 A144944 A144945 * A144947 A144948 A144949

Keyword

nonn

Author

Pierre CAMI, Sep 26 2008, Oct 16 2008

Status

approved