This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A175264 #12 Mar 11 2014 01:32:51
%S A175264 2,3,2,5,7,2,3,11,13,2,17,19,23,5,3,29,3,31,2,37,41,3,43,47,7,53,59,3,
%T A175264 61,2,3,67,5,71,73,3,79,3,83,3,89,3,97,101,3,103,5,107,109,5,113,3,3,
%U A175264 11,5,3,127,2,5,131,3,137,3,139,5,149,3,151,7,3,157,163,5,167,3,13,5,173,3
%N A175264 a(n) = the middle prime among the distinct primes dividing {the n-th positive integer divisible by exactly an odd number of distinct primes}.
%H A175264 Harvey P. Dale, <a href="/A175264/b175264.txt">Table of n, a(n) for n = 1..1000</a>
%e A175264 The 28th positive integer divisible by exactly an odd number of distinct primes is 60. 60 is factored as 2^2*3*5. The distinct primes dividing 60 are therefore 2, 3, and 5. Since the middle of these primes is 3, then a(28) = 3.
%t A175264 mp[n_]:=Module[{prs=Transpose[FactorInteger[n]][[1]],pos},pos= Floor[ Length[ prs]/2]+1;prs[[pos]]]; mp/@Select[Range[300],OddQ[PrimeNu[#]]&] (* _Harvey P. Dale_, Jun 20 2012 *)
%Y A175264 Cf. A030230
%K A175264 nonn
%O A175264 1,1
%A A175264 _Leroy Quet_, Mar 16 2010
%E A175264 More terms from _R. J. Mathar_, Oct 09 2010