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A056019
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Self-inverse infinite permutation which shows the position of each finite permutation's inverse permutation in A055089.
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13
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0, 1, 2, 4, 3, 5, 6, 7, 12, 18, 13, 19, 8, 10, 14, 20, 16, 22, 9, 11, 15, 21, 17, 23, 24, 25, 26, 28, 27, 29, 48, 49, 72, 96, 73, 97, 50, 52, 74, 98, 76, 100, 51, 53, 75, 99, 77, 101, 30, 31, 36, 42, 37, 43, 54, 55, 78, 102, 79, 103, 60, 66, 84, 108, 90, 114, 61, 67, 85
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OFFSET
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0,3
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COMMENTS
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PermRevLexRank and PermRevLexUnrank have been modified from the algorithms PermLexRank and PermLexUnrank presented in the book "Combinatorial Algorithms, Generation, Enumeration and Search", by Donald L. Kreher and Douglas R. Stinson.
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LINKS
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EXAMPLE
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E.g. the permutation [2,3,1] is the 4th permutation (counting from 0th, the identity permutation) of A055089, its inverse permutation is [3,1,2] which is 3rd, thus a(4)=3 and a(3)=4.
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MAPLE
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PermRevLexRank := proc(pp) local p, n, i, j, r; p := pp; n := nops(p); r := 0; for j from n by -1 to 1 do r := r + (((j-p[j])*((j-1)!))); for i from 1 to (j-1) do if(p[i] > p[j]) then p[i] := p[i]-1; fi; od; od; RETURN(r); end;
[seq(PermRevLexRank(convert(invperm(convert(PermRevLexUnrank(j), 'disjcyc')), 'permlist', nops(PermRevLexUnrank(j)))), j=0..200)];
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MATHEMATICA
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A056019 = Position[Ordering /@ #, #[[#2]]][[1, 1]] - 1 &[Reverse@SortBy[Permutations@Range@Ceiling@InverseFunction[Factorial][# + 1], Reverse], # + 1] &; Array[A056019, 69, 0] (* JungHwan Min, Oct 10 2016 *)
A056019L = Ordering[Ordering /@ Permutations@Range@Ceiling@InverseFunction[Factorial][# + 1]] - 1 &; A056019L[24] (* JungHwan Min, Oct 10 2016 *)
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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