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 A292070 #4 Sep 11 2017 20:06:19
%S A292070 41,2625641,4201025641,70481514601025641025641025641,
%T A292070 180432677378625641025641025641025641,
%U A292070 739052246542850625641025641025641025641025641
%N A292070 Primes of the form (40^k - 1) / 39.
%t A292070 Select[Table[(40^k - 1) / 39, {k, 0, 100}], PrimeQ[#] &]
%Y A292070 Cf. A128005.
%K A292070 nonn
%O A292070 1,1
%A A292070 _Robert Price_, Sep 08 2017