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 A082128 #9 Mar 11 2015 07:43:26 %S A082128 21,4,5,13,8,2,32,16,64,512,131072,4194304,8589934592, %T A082128 9007199254740992,75557863725914323419136, %U A082128 20769187434139310514121985316880384 %N A082128 Smallest difference>1 between d and p/d for any divisor d of the partial product p of the sequence, starting with 21. %C A082128 For n>3, the members are all powers of two. Proved by Luke Pebody, pers. comm. %o A082128 (PARI) p=21; print1(p, ", "); for(n=1, 50, v=divisors(p); r=sqrt(p); t=0; for(k=1, matsize(v)[2], if(v[k]>=r, t=k; break)); if(v[t]^2==p, u=t, u=t-1); if(v[t]-v[u]<2, u=u-1; t=t+1); print1(v[t]-v[u]", "); p=p*(v[t]-v[u])) %Y A082128 Cf. A082120, A003681 (starts with 2, 3). %K A082128 nonn,hard %O A082128 0,1 %A A082128 _Ralf Stephan_, Apr 04 2003