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 A144246 #13 Jul 24 2025 03:26:16
%S A144246 19,109,991,1009,10009,99991,9999991,1000000009,1000000000000000009,
%T A144246 10000000000000000000009,999999999999999999999999999999991,
%U A144246 999999999999999999999999999999999999999999991,1000000000000000000000000000000000000000000009
%N A144246 Prime numbers of the form 10^k +- 9.
%C A144246 This sequence illustrates the base-n representation of numbers having the form n^k +- (n - 1).
%H A144246 Amiram Eldar, <a href="/A144246/b144246.txt">Table of n, a(n) for n = 1..25</a>
%t A144246 Select[Sort[Flatten[Table[10^n+{9,-9},{n,50}]]],PrimeQ] (* _Harvey P. Dale_, Jul 22 2016 *)
%Y A144246 Cf. A000040, A000668, A144231, A144232, A144233, A144234, A144236, A144242, A144245.
%K A144246 nonn
%O A144246 1,1
%A A144246 _Reikku Kulon_, Sep 15 2008
%E A144246 a(13) from _Amiram Eldar_, Jul 24 2025