%I A075227
%S A075227 3,5,7,17,37,43,43,151,151,409,491,491,491,1087,2011,3709,3709,7417,
%T A075227 7417,7417
%N A075227 Smallest odd prime not occurring in the numerator of the 2^n sums generated 
               from the set 1, 1/2, 1/3,..., 1/n.
%C A075227 The largest prime generated is given in A075226. For information about 
               how often the numerator of these sums is prime, see A075188 and A075189.
%e A075227 a(3) = 7 because 7 is the smallest prime not occurring in the numerator 
               of the sums 1+1/2 = 3/2, 1/2+1/3 = 5/6 and 1+1/2+1/3 = 11/6.
%t A075227 Needs["DiscreteMath`Combinatorica`"]; maxN=20; For[lst={}; prms={}; i=0; 
               n=1, n<=maxN, n++, While[i<2^n-1, i++; s=NthSubset[i, Range[n]]; 
               k=Numerator[Plus@@(1/s)]; If[PrimeQ[k], AppendTo[prms, k]]]; prms=Union[prms]; 
               j=2; While[MemberQ[prms, Prime[j]], j++ ]; AppendTo[lst, Prime[j]]]; 
               lst
%Y A075227 Cf. A001008, A075135, A075188, A075189, A075226.
%Y A075227 Sequence in context: A016041 A140797 A038893 this_sequence A064080 A112986 
               A088732
%Y A075227 Adjacent sequences: A075224 A075225 A075226 this_sequence A075228 A075229 
               A075230
%K A075227 nice,nonn
%O A075227 1,1
%A A075227 T. D. Noe (noe(AT)sspectra.com), Sep 08 2002