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 A258581 #30 Aug 04 2015 10:13:15
%S A258581 2,3,2,5,2,3,23,37,17,149,761,50647,4799,411527,18871308021859,
%T A258581 10312625105789,17838863896549,57892815889963361050999657943,
%U A258581 2252973546284243766517,1849093263449444009859625443689931115519009693
%N A258581 a(1) = 2; for n > 1 if n is even a(n) = gpf(1 + Product_{odd m,m<n}a(m)), while if n is odd a(n) = gpf(1 + Product_{even m,m<n}a(m)).
%H A258581 Anders Hellström, <a href="https://oeis.org/wiki/User:Anders_Hellstr%C3%B6m/A258581.sage">Sage program</a>
%H A258581 Anders Hellström, <a href="https://oeis.org/wiki/User:Anders_Hellstr%C3%B6m/A258581.m">Mercury program</a>
%o A258581 (PARI) gpf(n)=my(v=factor(n)[, 1]); v[#v];
%o A258581 main(size)=my(v=vector(size), i, odd=2, even=1); v[1]=2; for(i=2, size, if(i%2==0, v[i]=gpf(odd+1); even*=v[i], v[i]=gpf(even+1); odd*=v[i])); v;
%Y A258581 Cf. A000946, A005266.
%K A258581 nonn
%O A258581 1,1
%A A258581 _Anders Hellström_, Jul 15 2015