cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A057513 Number of separate orbits to which permutations given in A057511/A057512 (induced by deep rotation of general parenthesizations/plane trees) partition each A000108(n) objects encoded by A014486 between (A014138(n-1)+1)-th and (A014138(n))-th terms.

Original entry on oeis.org

1, 1, 2, 4, 9, 21, 56, 153, 451, 1357, 4212, 13308, 42898, 140276, 465324, 1561955, 5300285, 18156813, 62732842, 218405402, 765657940
Offset: 0

Views

Author

Antti Karttunen Sep 03 2000

Keywords

Comments

It is much faster to compute this sequence empirically with the given C-program than to calculate the terms with the formula in its present form.

Crossrefs

CountCycles given in A057502, for other procedures, follow A057511 and A057501.
Similarly generated sequences: A001683, A002995, A003239, A038775, A057507. Cf. also A000081.
Occurs for first time in A073201 as row 12. Cf. A057546 and also A000081.

Programs

  • Maple
    A057513 := proc(n) local i; `if`((0=n),1,(1/A003418(n-1))*add(A079216bi(n,i),i=1..A003418(n-1))); end;
    # Or empirically:
    DeepRotatePermutationCycleCounts := proc(upto_n) local u,n,a,r,b; a := []; for n from 0 to upto_n do b := []; u := (binomial(2*n,n)/(n+1)); for r from 0 to u-1 do b := [op(b),1+CatalanRank(n,DeepRotateL(CatalanUnrank(n,r)))]; od; a := [op(a),CountCycles(b)]; od; RETURN(a); end;

Formula

a(0)=1, a(n) = (1/A003418(n-1))*Sum_{i=1..A003418(n-1)} A079216(n, i) [Needs improvement.] - Antti Karttunen, Jan 03 2003

A038776 The sequence a[1] to a[ cat[n] ] is the permutation that converts forest[n] of depth-first planar planted binary trees into breadth-first representation.

Original entry on oeis.org

1, 2, 4, 5, 3, 9, 10, 13, 14, 12, 6, 7, 8, 11, 23, 24, 27, 28, 26, 36, 37, 41, 42, 40, 32, 33, 35, 39, 15, 16, 18, 19, 17, 22, 25, 20, 21, 34, 38, 29, 30, 31, 65, 66, 69, 70, 68, 78, 79, 83, 84, 82, 74, 75, 77, 81, 106, 107, 111, 112, 110, 125, 126, 131, 132, 130
Offset: 1

Views

Author

Wouter Meeussen, May 04 2000

Keywords

Examples

			tree ( 1 (100) (10 ) ) becomes (1) (11)(00 0 ) thus (1 (1(100) 0) ) and is permuted from position 3 in forest[3] to position 5 by permutation {1,2,4,5,3}={{1},{2},{4,5,3}}
		

Crossrefs

Compare to the plot of A082364 and A072619.
Inverse of A070041. Cf. also A038774, A038775. If "expanded" produces A057117. Max cycle lengths: A057542.

Programs

  • Maple
    [seq(CatalanRank(inf,(btbf2df(binrev(CatalanUnrank(inf,j)),0,1)/2))+1,j=0..(binomial(2*inf,inf)/(inf+1))-1)]; (In practice, use a value like 6 instead of infinity).
    btbf2df := proc(nn,i,r) local n,j,c,x,y,w; n := nn; if(0 = (n mod 2)) then RETURN(0); fi; c := i; for j from 1 to r do c := c + (n mod 2); n := floor(n/2); od; w := 2*c; c := 0; for j from 1 to (2*i) do c := c + (n mod 2); n := floor(n/2); od; x := btbf2df(n,c,(w-(j-1))); y := btbf2df(floor(n/2),c+(n mod 2),(w-(j))); RETURN((2^(binwidth(x)+binwidth(y))) + (x * (2^(binwidth(y)))) + y); end;
    floor_log_2 := proc(n) local nn,i: nn := n; for i from -1 to n do if(0 = nn) then RETURN(i); fi: nn := floor(nn/2); od: end:
    binwidth := n -> (`if`((0 = n),1,floor_log_2(n)+1));
    binrev := proc(nn) local n,z; n := nn; z := 0; while(n <> 0) do z := 2*z + (n mod 2); n := floor(n/2); od; RETURN(z); end;
  • Mathematica
    bracket[ tree_ ] := (Flatten[ {tree, 0} ]/. 0->{0})//.{1, z___, 1, a_List, b_List, y___}:>{1, z, {1, a, b}, y}; widthfirst[ dectree_ ] := b2d[ Drop[ Flatten[ {Table[ Cases[ Level[ #, {k}, z ], A014486%20*)%20Ordering%5BReverse%5Bwidthfirst%20/@%20b2d%20/@%20wood%5B6%5D%5D%5D%20(*%20_Wouter%20Meeussen">Integer ], {k, Depth[ # ]-1} ] }/.z->List ], -1 ] ] & @(bracket@d2b[ dectree ]); (* uses functions in A014486 *) Ordering[Reverse[widthfirst /@ b2d /@ wood[6]]] (* _Wouter Meeussen, Aug 19 2025 *)

Extensions

Additional comments from Antti Karttunen, Aug 11 2000

A038774 Cycle lengths of the permutation that converts the forest of depth-first planar planted binary trees into breadth-first representation.

Original entry on oeis.org

1, 1, 3, 4, 3, 2, 16, 8, 2, 2, 87, 3, 202, 25, 5, 4, 61, 607, 63, 165, 127, 12, 8, 10, 4, 5, 927, 1441, 283, 625, 91, 52, 8, 5, 4708, 592, 1890, 86, 3505, 482, 471, 34, 84, 17, 22, 25, 5, 9, 3, 1
Offset: 1

Views

Author

Wouter Meeussen, May 04 2000

Keywords

Examples

			The first 6 terms add up to 14=cat[4], so the cycle lengths of the permutation for forest[4] are {1, 1, 3, 4, 3, 2}. The sequence as given (50 terms) was generated on forest[10].
		

Crossrefs

Cf. A038775, A038776. Max cycle lengths: A057542.
Showing 1-3 of 3 results.