A064638 Positions of non-crossing fixed-point-free involutions encoded by A014486 in A055089. Permutation of A064640.

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

Offset

0,3

Links

Table of n, a(n) for n=0..35.

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

Adjacent sequences: A064635 A064636 A064637 * A064639 A064640 A064641

Keyword

nonn

Author

Antti Karttunen, Oct 02 2001

Status

approved