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 A057501 Signature-permutation of a Catalan Automorphism: Rotate non-crossing chords (handshake) arrangements; rotate the root position of general trees as encoded by A014486. 40
 0, 1, 3, 2, 7, 8, 5, 4, 6, 17, 18, 20, 21, 22, 12, 13, 10, 9, 11, 15, 14, 16, 19, 45, 46, 48, 49, 50, 54, 55, 57, 58, 59, 61, 62, 63, 64, 31, 32, 34, 35, 36, 26, 27, 24, 23, 25, 29, 28, 30, 33, 40, 41, 38, 37, 39, 43, 42, 44, 47, 52, 51, 53, 56, 60, 129, 130, 132, 133, 134 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS This is a permutation of natural numbers induced when "noncrossing handshakes", i.e., Stanley's interpretation (n), "n nonintersecting chords joining 2n points on the circumference of a circle", are rotated. The same permutation is induced when the root position of plane trees (Stanley's interpretation (e)) is successively changed around the vertices. For a good illustration how the rotation of the root vertex works, please see the Figure 6, "Rotation of an ordered rooted tree" in Torsten Mütze's paper (on page 24 in 20 May 2014 revision). For yet another application of this permutation, please see the attached notes for A085197. By "recursivizing" either the left or right hand side argument of A085201 in the formula, one ends either with A057161 or A057503. By "recursivizing" the both sides, one ends with A057505. - Antti Karttunen, Jun 06 2014 LINKS Antti Karttunen, Table of n, a(n) for n = 0..2055 A. Karttunen, Introductory Survey of Catalan Automorphisms and Bijections (an unfinished draft), pp. 56-57. A. Karttunen et al, Combinatorial interpretations of Catalan numbers, OEIS Wiki. Torsten Mütze, Proof of the middle levels conjecture, arXiv preprint arXiv:1404.4442 [math.CO], 2014 (p. 24). R. P. Stanley, Exercises on Catalan and Related Numbers (This sequence is concerned with rotations of the interpretations (e) and (n) in the Exercise 19) FORMULA a(0) = 0, and for n>=1, a(n) = A085201(A072771(n), A057548(A072772(n))). [This formula reflects directly the given non-destructive Lisp/Scheme function: A085201 is a 2-ary function corresponding to 'append', A072771 and A072772 correspond to 'car' and 'cdr' (known also as first/rest or head/tail in some dialects), and A057548 corresponds to unary form of function 'list']. As a composition of related permutations: a(n) = A057509(A069770(n)). a(n) = A057163(A069773(A057163(n))). Invariance-identities: A129599(a(n)) = A129599(n) holds for all n. MAPLE map(CatalanRankGlobal, map(RotateHandshakes, A014486)); RotateHandshakes := n -> pars2binexp(RotateHandshakesP(binexp2pars(n))); RotateHandshakesP := h -> `if`((0 = nops(h)), h, [op(car(h)), cdr(h)]); # This does the trick! In Lisp: (defun RotateHandshakesP (h) (append (car h) (list (cdr h)))) car := proc(a) if 0 = nops(a) then ([]) else (op(1, a)): fi: end: # The name is from Lisp, takes the first element (head) of the list. cdr := proc(a) if 0 = nops(a) then ([]) else (a[2..nops(a)]): fi: end: # As well. Takes the rest (the tail) of the list. PeelNextBalSubSeq := proc(nn) local n, z, c; if(0 = nn) then RETURN(0); fi; n := nn; c := 0; z := 0; while(1 = 1) do z := 2*z + (n mod 2); c := c + (-1)^n; n := floor(n/2); if(c >= 0) then RETURN((z - 2^(floor_log_2(z)))/2); fi; od; end; RestBalSubSeq := proc(nn) local n, z, c; n := nn; c := 0; while(1 = 1) do c := c + (-1)^n; n := floor(n/2); if(c >= 0) then break; fi; od; z := 0; c := -1; while(1 = 1) do z := 2*z + (n mod 2); c := c + (-1)^n; n := floor(n/2); if(c >= 0) then RETURN(z/2); fi; od; end; pars2binexp := proc(p) local e, s, w, x; if(0 = nops(p)) then RETURN(0); fi; e := 0; for s in p do x := pars2binexp(s); w := floor_log_2(x); e := e * 2^(w+3) + 2^(w+2) + 2*x; od; RETURN(e); end; binexp2pars := proc(n) option remember; `if`((0 = n), [], binexp2parsR(binrev(n))); end; binexp2parsR := n -> [binexp2pars(PeelNextBalSubSeq(n)), op(binexp2pars(RestBalSubSeq(n)))]; # Procedure CatalanRankGlobal given in A057117, other missing ones in A038776. PROG (Scheme functions implementing this automorphism on S-expressions, "constructive" and "destructive" variants): (define (*A057501 s) (cond ((null? s) (list)) (else (append (car s) (list (cdr s)))))) (define (*A057501! s) (cond ((pair? s) (*A074680! s) (*A057501! (cdr s)))) s) ;; A version working directly on nonnegative integers (definec is a memoization macro from Antti Karttunen's IntSeq-library): (definec (A057501 n) (if (zero? n) n (A085201bi (A072771 n) (A057548 (A072772 n))))) ;; A085201bi, see: A085201. CROSSREFS Inverse: A057502. Also, a "SPINE"-transform of A074680, and thus occurs as row 17 of A122203. (Also as row 65167 of A130403.) Successive powers of this permutation, a^2(n) - a^6(n): A082315, A082317, A082319, A082321, A082323. Other related permutations: A057161, A057163, A057503, A057505, A057508, A057509, A057511, A069770, A069771, A069772, A069773, A069888, A069889, A082313, A082314, A085173, A086427, A123501, A127291, A127292. Cf. also A057548, A072771, A072772, A085201, A002995 (cycle counts), A057543 (max cycle lengths), A085197, A129599, A057517, A064638, A064640. Sequence in context: A130955 A129610 A130923 * A071655 A130964 A130929 Adjacent sequences:  A057498 A057499 A057500 * A057502 A057503 A057504 KEYWORD nonn AUTHOR Antti Karttunen, Sep 03 2000; entry revised Jun 06 2014 STATUS approved

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Last modified December 6 19:31 EST 2019. Contains 329809 sequences. (Running on oeis4.)