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 A323948 #4 Feb 13 2019 08:39:52 %S A323948 1,2,4,8,26,31,64,156,218,521,1048,2014,4096,8291,26384,31768,65536, %T A323948 161244,232071,514188,1097251,2048576,4294304,8388608,26777126, %U A323948 33554431,67208864,168435456,234127718,536870921,1247483648,2073742814,4194967196,8589934591,27279869284,34359738368,68729476736,174877906944 %N A323948 The numbers 2^n with 1's and 2's swapped, then sorted. %Y A323948 Cf. A000079, A306392. %K A323948 nonn,base %O A323948 0,2 %A A323948 _N. J. A. Sloane_, Feb 13 2019