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 A206798 #9 Mar 13 2015 22:56:26
%S A206798 4,6,8,1,9,2,10,3,5,7,12,11,14,13,17,19,15,23,16,29,31,37,18,41,43,47,
%T A206798 53,59,20,61,21,67,71,73,79,83,22,89,97,101,24,103,25,107,109,113,26,
%U A206798 127,131,137,139,149,27,151,157,163,167,173,28,179,30,181,191
%N A206798 Beginning with the natural numbers, swap the k-th composite number (A002808) and k-th noncomposite number (A008578), for k = 1,2,3,...
%C A206798 Sequence is self-inverse permutation of natural numbers. Also swap sequence of pair of complements A002808 and A008578.
%F A206798 a(n) = A181097(n) for first 14 terms.
%e A206798 a(7) = 10 becauce number 7 is 5th term of sequence A008578 and 5th term of sequence A002808 is number 10.
%t A206798 nn = 191; t1 = Select[Range[nn], # == 1 || PrimeQ[#] &]; t2 = Complement[Range[nn], t1]; t = Range[nn]; Do[temp = t[[t1[[i]]]]; t[[t1[[i]]]] = t[[t2[[i]]]]; t[[t2[[i]]]] = temp, {i, Length[t1]}]; Take[t, Position[t, t1[[-1]]][[1, 1]]] (* _T. D. Noe_, Feb 13 2012 *)
%Y A206798 Cf. A026234 (swap the k-th prime and k-th nonprime, for k = 1,2,3,...).
%K A206798 nonn
%O A206798 1,1
%A A206798 _Jaroslav Krizek_, Feb 12 2012