Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #4 Mar 31 2012 14:40:18
%S 0,50,75,75,75,78,78,77,75,72,70,66,64,61,59,57,55,53,51,49,48,46,45,
%T 43,42,41,40,39,38,37,36,35,34
%N Percentage (rounded) of odd numbers < 2^n which are primes or squarefree semiprimes.
%F a(n) = round((A146168(n)+A007053(n)-1)/(2^(n-1))*100).
%e a(4)=75 because 75% of the 2^3 numbers 1, 3, 5, 7, 9, 11, 13 and 15 are primes or squarefree semiprimes.
%Y Cf. A001358(semiprimes), A007053(Number of primes <= 2^n), A146168(Number of odd squarefree semiprimes < 2^n).
%K nonn
%O 1,2
%A _Washington Bomfim_, Oct 27 2008