1,1

1*4+1=5

3*4+1=13

9*4+1=37

27*4+1=109; 5,13,37,109 are all prime so k(1)=4

Cf. A112042, A112043.

Sequence in context: A058173 A074835 A060492 this_sequence A002060 A007220 A034866

Adjacent sequences: A112038 A112039 A112040 this_sequence A112042 A112043 A112044

nonn

Pierre CAMI (pierrecami(AT)tele2.fr), Aug 26 2005