1,1

a(n) = A000042(A046413(n-1)). - Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 06 2005

a(2)=1111 because 1111=11*101, so 1111 is semiprime as well as a repunit number.

Cf. A046413 the repunit of length n has exactly 2 prime factors.

Adjacent sequences: A102779 A102780 A102781 this_sequence A102783 A102784 A102785

Sequence in context: A115875 A115816 A115877 this_sequence A137465 A101152 A075859

base,nonn

Shyam Sunder Gupta (guptass(AT)rediffmail.com), Feb 11 2005