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A064638 Positions of non-crossing fixed-point-free involutions encoded by A014486 in A055089. Permutation of A064640. 3
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; text; internal format)
OFFSET
0,3
LINKS
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;
CROSSREFS
Maple procedure binexp2pars given in A057501, permul in A060125.
Sequence in context: A228698 A064640 A064639 * A082021 A227254 A080082
KEYWORD
nonn
AUTHOR
_Antti Karttunen_, Oct 02 2001
STATUS
approved

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Last modified May 23 15:34 EDT 2024. Contains 372763 sequences. (Running on oeis4.)