1,1
Table of n, a(n) for n=1..65.
1*(2^3)-1=7 prime so a(1)=2
2*(2^3)-1=15 composite
2*((2*3)^3)-1=431 prime so a(2)=3
Sequence in context: A163873 A292588 A225176 * A225243 A207338 A027746
Adjacent sequences: A118662 A118663 A118664 * A118666 A118667 A118668
nonn
Pierre CAMI, May 19 2006
approved