OFFSET
1,1
FORMULA
EXAMPLE
a(1)=2 because 1st semiprime = 4 = 100_2.
a(2)=1 because 2nd semiprime = 6 = 110_2.
MAPLE
MATHEMATICA
DigitCount[#, 2, 0] & /@ Select[Range@ 328, PrimeOmega@ # == 2 &] (* Michael De Vlieger, Feb 02 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, May 18 2010
EXTENSIONS
a(56) corrected by R. J. Mathar, May 23 2010
STATUS
approved