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 A064039 #3 May 01 2014 02:48:25 %S A064039 0,1,10,11,21,20,100,101,110,111,121,120,210,211,200,201,220,221,311, %T A064039 310,321,320,301,300,1000,1001,1010,1011,1021,1020,1100,1101,1110, %U A064039 1111,1121,1120,1210,1211,1200,1201,1220,1221,1311,1310,1321,1320,1301,1300 %N A064039 Reversed inversion vectors for the permutations of A060117, presented as pseudo-decimal numbers. %C A064039 If one uses the ordering of A055089 instead of A060117 (procedure PermRevLexUnrank instead of PermUnrank3R) one gets A007623 (Integers written in factorial base) which is a permutation of this sequence. %p A064039 [seq(SiteSwap2ToDec(Perm2InversionVector(PermUnrank3R(j))),j=0..119)]; %p A064039 Perm2InversionVector := proc(p) local n,i,j,a,c; n := nops(p); a := []; for i from 2 to n do c := 0; for j from 1 to i-1 do if(p[j] > p[i] then c := c+1; fi; od; a := [op(a),c]; od; RETURN(a); end; %Y A064039 SiteSwap2ToDec procedure given in A060496 and PermUnrank3R in A060117. %K A064039 nonn,base %O A064039 1,3 %A A064039 _Antti Karttunen_, Aug 23 2001