1,1
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
Adjacent sequences: A118662 A118663 A118664 this_sequence A118666 A118667 A118668
Sequence in context: A002307 A029247 A053269 this_sequence A027746 A128651 A093797
nonn
Pierre CAMI (pierrecami(AT)tele2.fr), May 19 2006
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