1,2
The 5th prime number is 11. The binary representation of 11 is 1011. There are 3 "1s" in 1011. 3 in binary is 11, so a(5)=3.
Sequence in context: A166710 A003855 A004209 this_sequence A112867 A063697 A111381
Adjacent sequences: A162717 A162718 A162719 this_sequence A162721 A162722 A162723
base,nonn
Ben Branman (137ben(AT)comcast.net), Jul 11 2009
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