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 A304734 #9 Dec 20 2021 05:27:12 %S A304734 1,1,2,1,2,3,4,3,1,2,3,5,1,2,3,6,4,4,1,2,3,7,5,6,4,5,1,2,3,8,5,1,2,3, %T A304734 6,1,2,3,7,8,4,1,2,3,9,9,4,10,7,8,9,10,5,5,10,1,2,3,6,1,2,3,11,6,4,1, %U A304734 2,3,11,6,4,12,1,2,3,12,11,7,8,1,2,3,13,5,5,14,4,1,2,3,13,12,7,8,6,9,13,14,1,2,3,6,10,14,4 %N A304734 Ordinal transform of the largest prime factor of the n-th term of EKG-sequence. %C A304734 Ordinal transform of A304733(n) = A006530(A064413(n)). %H A304734 Antti Karttunen, <a href="/A304734/b304734.txt">Table of n, a(n) for n = 1..20090</a> %H A304734 <a href="/index/Ed#EKG">Index entries for sequences related to EKG sequence</a> %t A304734 terms = 105; %t A304734 ekGrapher[s_List] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]]; %t A304734 A304733 = FactorInteger[#][[-1, 1]]& /@ Nest[ekGrapher, {1, 2}, terms]; %t A304734 b[_] = 0; %t A304734 a[n_] := a[n] = With[{t = A304733[[n]]}, b[t] = b[t]+1]; %t A304734 Array[a, terms] (* _Jean-François Alcover_, Dec 20 2021, after _Robert G. Wilson v_ in A064413 *) %o A304734 (PARI) %o A304734 A006530(n) = if(n>1, vecmax(factor(n)[, 1]), 1); %o A304734 A304733(n) = A006530(A064413(n)); \\ Needs also code for A064413. %o A304734 ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om,invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om,invec[i],(1+pt))); outvec; }; %o A304734 v304734 = ordinal_transform(vector(65539,n,A304733(n))); %o A304734 A304734(n) = v304734[n]; %Y A304734 Cf. A006530, A064413, A064741, A304733. %Y A304734 Cf. also A078899. %K A304734 nonn,look %O A304734 1,3 %A A304734 _Antti Karttunen_, May 18 2018