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 A259255 #8 Jun 22 2015 19:05:02
%S A259255 1,2,5,17,13,97,3077,155333,147223992353,182758163483477540989,
%T A259255 634072602906397751091977058984828897557
%N A259255 With a(1) = 1, a(n) is the smallest number not already in the sequence such that -1 + Product_{i=1..n} a(i) is a square.
%o A259255 (PARI) v=[1];n=1;while(n<10^6,s=-1+n*prod(i=1,#v,v[i]);if(issquare(s)&&! vecsearch(vecsort(v),n),v=concat(v,n);n=0);n++);v
%Y A259255 Cf. A094353, A083275.
%K A259255 nonn,hard,more
%O A259255 1,2
%A A259255 _Derek Orr_, Jun 22 2015
%E A259255 a(9)-a(11) from _Giovanni Resta_, Jun 22 2015