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 A105145 #12 Apr 29 2018 18:43:56
%S A105145 18,21,30,32,39,71,72,78,84,86,89,93,95,98,107,108,135,143,150,152,
%T A105145 159,161,165,170,173,177,179,180,192,198,203,221,243,245,248,261,269,
%U A105145 281,282,294,302,306,315,320,329,336,338,347,369,374,378,395,399,423,425,443,446,449,456,458,471,500,504
%N A105145 Numbers n such that the string n10001 is prime.
%H A105145 Harvey P. Dale, <a href="/A105145/b105145.txt">Table of n, a(n) for n = 1..1000</a>
%e A105145 If n=18, then n10001 = 1810001 (prime).
%e A105145 If n=98, then n10001 = 9810001 (prime).
%p A105145 read("transforms") :
%p A105145 for n from 1 to 1000 do p := digcat2(n,10001) ; if isprime(p) then printf("%d,",n); end if; end do: # _R. J. Mathar_, Feb 02 2011
%t A105145 Select[Range[600],PrimeQ[#*10^5+10001]&] (* _Harvey P. Dale_, Apr 29 2018 *)
%Y A105145 Cf. A105106, A105107.
%K A105145 base,nonn,easy
%O A105145 1,1
%A A105145 _Parthasarathy Nambi_, Apr 09 2005