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 A305973 #7 Jun 16 2018 18:31:06
%S A305973 1,2,2,2,3,2,2,4,2,2,4,2,3,5,2,2,4,4,2,4,2,2,6,2,3,4,2,4,4,2,2,6,4,2,
%T A305973 4,2,2,6,4,2,7,2,4,4,2,4,4,4,2,6,2,2,8,2,2,4,2,4,6,4,3,4,5,2,4,2,4,9,
%U A305973 2,2,4,4,4,6,2,2,6,4,2,4,4,2,8,2,3,6,2,6,4,2,2,4,4,4,9,2,2,8,2,2,4,4,4,6,4,2,4,4,4,4,4,2,10,2,2,8,2,4,4,2
%N A305973 Filter sequence for the prime signature of 2n-1.
%C A305973 Restricted growth sequence transform of A278223, the least number with the same prime signature as the n-th odd number.
%H A305973 Antti Karttunen, <a href="/A305973/b305973.txt">Table of n, a(n) for n = 1..65537</a>
%o A305973 (PARI)
%o A305973 up_to = 65537;
%o A305973 rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
%o A305973 A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ From A046523
%o A305973 v305973 = rgs_transform(vector(up_to,n,A046523(n+n-1)));
%o A305973 A305973(n) = v305973[n];
%Y A305973 Cf. A046523, A101296, A278223, A305901, A305983, A305985.
%K A305973 nonn
%O A305973 1,2
%A A305973 _Antti Karttunen_, Jun 15 2018