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 A066646 #7 Mar 15 2021 01:48:53
%S A066646 1,2,3,6,7,8,15,17,22,24,25,26,27,30,55,56,61,68,81,83,87,95,106,108,
%T A066646 112,120,121,122,123,126,127,128,135,137,142,144,265,266,267,270,289,
%U A066646 290,315,317,340,342,391,392,397,404,415,416,445,451,470,476,513,515
%N A066646 Arrange the permutations of {1..m} in lexicographic order. Sequence gives indices of permutations of orders 1 or 2.
%C A066646 Independent of choice of m as long as m! exceeds index.
%e A066646 Take m=4, say. The first few permutations are 1234, 1243, 1324, 1342, 1423, 1432, 2134, 2143, 2314, ... and numbers 1,2,3,6,7,8,... have orders 1 or 2. This gives the first 6 terms.
%K A066646 easy,nice,nonn
%O A066646 1,2
%A A066646 _Ian Mooney_, Jan 09 2002