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 A305983 #10 Jun 16 2018 18:31:32 %S A305983 1,2,2,3,2,4,2,5,3,4,2,6,2,7,4,8,2,9,2,10,7,4,2,11,3,12,4,10,2,13,2, %T A305983 10,4,7,7,14,2,7,12,15,2,13,2,16,9,4,2,17,18,19,7,20,2,13,4,21,7,4,2, %U A305983 22,2,23,24,25,12,26,2,27,4,28,2,29,2,23,24,27,7,30,2,31,32,4,2,33,7,7,4,34,2,35,36,10,23,7,7,37,2,38,9,39,2,28,2,40,13 %N A305983 Filter sequence combining from all proper divisors d of n, the prime signature of 2d+1. %C A305983 Restricted growth sequence transform of A305982. %C A305983 For all i, j: a(i) = a(j) => A305818(i) = A305818(j). %H A305983 Antti Karttunen, <a href="/A305983/b305983.txt">Table of n, a(n) for n = 1..65537</a> %o A305983 (PARI) %o A305983 up_to = 65537; %o A305983 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 A305983 A305982(n) = { my(m=1); fordiv(n, d, if((d<n), m *= prime(A305973(1+d)-1))); (m); }; \\ Needs also code from A305973. %o A305983 v305983 = rgs_transform(vector(up_to,n,A305982(n))); %o A305983 A305983(n) = v305983[n]; %Y A305983 Cf. A305973, A305982, A305985. %K A305983 nonn %O A305983 1,2 %A A305983 _Antti Karttunen_, Jun 15 2018