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 A100759 #7 Aug 26 2015 23:47:58
%S A100759 2,7,5,17,127,3,347,37,71,829,89,79,311,271,1103,823,827,7219,149,499,
%T A100759 3947,6367,2861,3673,13781,2281,281,229,353,1597,191,1879,2609,10993,
%U A100759 19961,4789,383,1093,521,13681,9227,12619,8219,12037,8573,7621,6029
%N A100759 Beginning with 2, least prime not occurring earlier such that the concatenation of first n terms has the least prime factor prime(n).
%C A100759 Conjecture: Every prime is a member.
%e A100759 a(1) = 2, a(2) = 7 and the least prime divisor of 27 is 3.
%t A100759 a = {2}; b = 2; Do[i = 1; While[Length[Intersection[a, {Prime[i]}]] == 1, i++ ]; While[ !FactorInteger[FromDigits[Join[IntegerDigits[b], IntegerDigits[Prime[i]]]]][[1, 1]] == Prime[n], i++ ]; AppendTo[a, Prime[i]]; b = FromDigits[Join[IntegerDigits[b], IntegerDigits[Prime[i]]]], {n, 2, 30}]; a (* _Stefan Steinerberger_, Dec 21 2007 *)
%Y A100759 Cf. A114025.
%K A100759 base,less,nonn
%O A100759 1,1
%A A100759 _Amarnath Murthy_, Nov 23 2004
%E A100759 More terms from _Stefan Steinerberger_, Dec 21 2007
%E A100759 More terms from _David Wasserman_, Mar 04 2008