1,1

Table of n, a(n) for n=1..20.

2*(2^2-1)*(2^3-1)*(2^5-1) - 1 = 1301 prime so k(3)=2

Sequence in context: A025521 A305109 A068218 * A161748 A195871 A214756

Adjacent sequences: A098916 A098917 A098918 * A098920 A098921 A098922

hard,more,nonn

Pierre CAMI, Oct 17 2004

a(15)-a(20) from Donovan Johnson, Mar 23 2008

approved