0,1

Since A001097(2)=5 is the only number to be member of two twin prime pairs, all terms of this sequence are lower twin primes A001359(k), k = 1,6,51,501,5001,..., cf. the given formula.

a(n) = A001359([10^n/2]+1)

Cf. A146214.

Sequence in context: A012104 A012147 A012011 this_sequence A139161 A057013 A055755

Adjacent sequences: A147794 A147795 A147796 this_sequence A147798 A147799 A147800

more,nonn

M. F. Hasler (MHasler(AT)univ-ag.fr), Dec 06 2008