1,1

5 belongs in the sequence because GCD( 5, P_5^2 -1) = GCD( 5, 120) = 5.

Do[ If[ GCD[ Prime[n], Prime[ Prime[n]]^2 - 1] != 1, Print[ Prime[n]] ], {n, 1, 10^6} ]

Cf. A064830.

Sequence in context: A067799 A117702 A041343 this_sequence A041655 A082520 A062597

Adjacent sequences: A064933 A064934 A064935 this_sequence A064937 A064938 A064939

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 26 2001