0,2

Conjecture: 4 and 9 are the only composite terms.

No more composite terms below 1.5e18. Such a term would require a prime gap greater than sqrt(p); in the absence of such large gaps, a(n) = prime(n-2) for n > 6. - Charles R Greathouse IV, Apr 12 2010

Table of n, a(n) for n=0..59.

4 is a member as phi(4)=2 and phi(1), phi(2), phi(3) are <= 2. 16 is not a member as phi(16) < phi(11).

Sequence in context: A001092 A000430 A166684 * A274197 A286267 A008750

Adjacent sequences: A067123 A067124 A067125 * A067127 A067128 A067129

easy,nonn

Amarnath Murthy, Jan 09 2002

approved