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A064638
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Positions of non-crossing fixed-point-free involutions encoded by A014486 in A055089. Permutation of A064640.
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2
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0, 1, 7, 23, 127, 415, 143, 659, 719, 5167, 16687, 5455, 26815, 28495, 5183, 16703, 5699, 36899, 38579, 5759, 36959, 40031, 40319, 368047, 1174447, 379567, 1901647, 1992367, 368335, 1174735, 389695, 2627455, 2718175, 391375, 2629135, 2799055
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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MAPLE
| map(PermRevLexRank, map(NonCrossingTranspos, A014486));
NonCrossingTranspos := n -> convert(NonCrossingTransposAux(binexp2pars(n), 1), 'permlist', binwidth(n));
NonCrossingTransposAux := proc(s, ii) local e, p, i, j; i := ii; p := []; for e in s do p := permul(p, NonCrossingTransposAux(e, i+1)); j := i+CountParens(e)+1; p := permul(p, [[i, j]]); i := j+1; od; RETURN(p); end;
CountParens := proc(s) local e, k; if(0 = nops(s)) then RETURN(0); fi; e := 0; for k in s do e := e+2+CountParens(k); od; RETURN(e); end;
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CROSSREFS
| Maple procedure binexp2pars given in A057501, permul in A060125.
Sequence in context: A137367 A064640 A064639 * A082021 A080082 A158954
Adjacent sequences: A064635 A064636 A064637 * A064639 A064640 A064641
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KEYWORD
| nonn
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AUTHOR
| Antti Karttunen Oct 02 2001
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