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 A105433 #10 Jan 17 2019 13:44:08
%S A105433 3,23,3,13,3,461,3,13,1163,3,19,1077697,3,13,29,3,31,3,13,1297561,3,
%T A105433 81703,53,3,13,1867,3,19,6053,3,13,163,3,1733,1954503644062423429,3,
%U A105433 13,33142829,3,79,24733371888243845161,3,13,193367,3,19,501654709,3,13
%N A105433 Smallest prime dividing the composite number consisting of n 1's followed by a terminal 3, where n=A105432.
%H A105433 Makoto Kamada, <a href="https://stdkmd.net/nrr/1/11113.htm">Factorizations of 11...113</a>.
%t A105433 FactorInteger[#][[1,1]]&/@Select[Table[FromDigits[PadLeft[{3},n,1]],{n,60}],!PrimeQ[#]&] (* _Harvey P. Dale_, Jun 04 2012 *)
%K A105433 nonn
%O A105433 1,1
%A A105433 _Lekraj Beedassy_, Apr 08 2005