1,2

Is the sequence finite?

Table of n, a(n) for n=1..24.

a(4)= 4 and the primes arising are 5, 7, 11, and 13.

Cf. A020498.

Sequence in context: A220521 A236680 A162798 * A097154 A108421 A104058

Adjacent sequences: A088647 A088648 A088649 * A088651 A088652 A088653

more,nonn

Amarnath Murthy, Oct 29 2003

Corrected and extended by Max Alekseyev, Aug 23 2013

approved