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 A050739 #5 Oct 16 2019 01:12:33 %S A050739 1,9,81,729,6561,59049,4782969,43046721,387420489,31381059609, %T A050739 282429536481,2541865828329,109418989131512359209, %U A050739 30903154382632612361920641803529 %N A050739 Numbers of form 9^k (values of k see A050730) containing no pair of consecutive equal digits (probably finite). %Y A050739 Cf. A043096, A050730. %K A050739 nonn,base %O A050739 0,2 %A A050739 _Patrick De Geest_, Sep 15 1999