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 1-5 of 5 results.

A057549 The local ranks of each term of A057547.

Original entry on oeis.org

0, 1, 3, 4, 8, 9, 11, 12, 13, 22, 23, 25, 26, 27, 31, 32, 34, 35, 36, 38, 39, 40, 41, 64, 65, 67, 68, 69, 73, 74, 76, 77, 78, 80, 81, 82, 83, 92, 93, 95, 96, 97, 101, 102, 104, 105, 106, 108, 109, 110, 111, 115, 116, 118, 119, 120, 122, 123, 124, 125, 127, 128, 129
Offset: 0

Views

Author

Antti Karttunen, Sep 07 2000

Keywords

Crossrefs

Formula

a(n) = CatalanRank(floor(binwidth(A057547[n])/2), A057547[n])

A057548 A014486-indices of Catalan mountain ranges with no sea-level valleys, i.e., the rooted plane general trees with root degree = 1.

Original entry on oeis.org

1, 3, 7, 8, 17, 18, 20, 21, 22, 45, 46, 48, 49, 50, 54, 55, 57, 58, 59, 61, 62, 63, 64, 129, 130, 132, 133, 134, 138, 139, 141, 142, 143, 145, 146, 147, 148, 157, 158, 160, 161, 162, 166, 167, 169, 170, 171, 173, 174, 175, 176, 180, 181, 183, 184, 185, 187, 188
Offset: 0

Views

Author

Antti Karttunen, Sep 07 2000

Keywords

Comments

This sequence is induced by the unary form of function 'list' (present in Lisp and Scheme) when it acts on symbolless S-expressions encoded by A014486/A063171.

Crossrefs

We have A057515(A057548(n)) = 1 for all n. Row 0 of A072764. Column 1 of A085203. Cf. A057517, A057549, A057551.

Formula

a(n) = A080300(A057547(n)) = A069770(A072795(n)).

A079946 Numbers k whose binary expansion begins with two or more 1's and ends with at least one 0.

Original entry on oeis.org

6, 12, 14, 24, 26, 28, 30, 48, 50, 52, 54, 56, 58, 60, 62, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124, 126, 192, 194, 196, 198, 200, 202, 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246
Offset: 1

Views

Author

N. J. A. Sloane, Feb 21 2003

Keywords

Comments

a(n) = b(n+1), with b(2n) = 2b(n), b(2n+1) = 2b(n)+2+4[n==0]. - Ralf Stephan, Oct 11 2003

Crossrefs

A004755 = union of this and A080565. A057547(n) = a(A014486(n)) for n >= 1.

Programs

  • Maple
    A079946 := n -> 2*(2^(1+A000523(n))+n);
  • Mathematica
    Table[Union[FromDigits[Join[{1,1},#,{0}],2]&/@Tuples[{1,0},n]],{n,0,5}]//Flatten (* Harvey P. Dale, Jan 16 2018 *)
  • PARI
    for(n=0,6, for(k=2^(n-1),2^n-1,print1((2^n+k)*2,",")))
    
  • PARI
    for(n=1,59,print1((2^(floor(log(n)/log(2))+1)+n)*2,","))
    
  • PARI
    a(n) = n*2 + 4<Ruud H.G. van Tol, May 10 2024
    
  • Python
    def A079946(n): return n+(1<Chai Wah Wu, Jul 13 2022

Formula

a(n) = 2^floor(log_2(4*n))+2*n. - Antonio G. Astudillo (afg_astudillo(AT)hotmail.com), Feb 22 2003
a(n) = (2^(floor(log_2(n))+1)+n)*2. - Klaus Brockhaus, Feb 23 2003
a(2n) = 2a(n), a(2n+1) = 2a(n) + 2 + 4[n==0]. Twice A004755. - Ralf Stephan, Oct 12 2003

Extensions

Definition clarified by N. J. A. Sloane, May 10 2024

A057517 Binary encodings of the Catalan mountain ranges with exactly one sea-level valley, i.e., the rooted plane trees with root degree = 2.

Original entry on oeis.org

10, 44, 50, 180, 184, 204, 210, 226, 724, 728, 740, 744, 752, 820, 824, 844, 850, 866, 908, 914, 930, 962, 2900, 2904, 2916, 2920, 2928, 2964, 2968, 2980, 2984, 2992, 3012, 3016, 3024, 3040, 3284, 3288, 3300, 3304, 3312, 3380, 3384, 3404, 3410, 3426
Offset: 1

Views

Author

Antti Karttunen, Sep 03 2000

Keywords

Comments

This bijective mapping from all rooted plane trees to one node larger, root degree = 2 trees illustrates the fact that CONV(A000108, A000108) = LEFT(A000108). (Catalan numbers shift left under convolution).

Crossrefs

Cf. A057501 (for binexp2pars, pars2binexp, car, cdr), A057518, A057519, A057122. Single-trunked trees: A057547.

Programs

  • Maple
    alltrees2doubletrunked := n -> pars2binexp(alltrees2doubletrunkedP(binexp2pars(n)));
    alltrees2doubletrunkedP := h -> [car(h),cdr(h)];

Formula

a(n) = alltrees2doubletrunked(A014486(n)) (Starting from n=1).

A216648 Triangle T(n,k) in which n-th row lists in increasing order all positive integers with a representation as totally balanced 2n digit binary string without totally balanced proper prefixes such that all consecutive totally balanced substrings are in nondecreasing order; n>=1, 1<=k<=A000081(n).

Original entry on oeis.org

2, 12, 52, 56, 212, 216, 232, 240, 852, 856, 872, 880, 920, 936, 944, 976, 992, 3412, 3416, 3432, 3440, 3480, 3496, 3504, 3536, 3552, 3688, 3696, 3752, 3760, 3792, 3808, 3888, 3920, 3936, 4000, 4032, 13652, 13656, 13672, 13680, 13720, 13736, 13744, 13776
Offset: 1

Views

Author

Alois P. Heinz, Sep 12 2012

Keywords

Comments

There is a simple bijection between the elements of row n and the rooted trees with n nodes. Each matching pair (1,0) in the binary string representation encodes a node, each totally balanced substring encodes a list of subtrees.

Examples

			856 is element of row 5, the binary string representation (with totally balanced substrings enclosed in parentheses) is (1(10)(10)(1(10)0)0).  The encoded rooted tree is:
.    o
.   /|\
.  o o o
.      |
.      o
Triangle T(n,k) begins:
2;
12;
52,     56;
212,   216,  232,  240;
852,   856,  872,  880,  920,  936,  944,  976,  992;
3412, 3416, 3432, 3440, 3480, 3496, 3504, 3536, 3552, 3688, 3696, ...
Triangle T(n,k) in binary:
10;
1100;
110100,       111000;
11010100,     11011000,     11101000,     11110000;
1101010100,   1101011000,   1101101000,   1101110000,   1110011000, ...
110101010100, 110101011000, 110101101000, 110101110000, 110110011000, ...
		

Crossrefs

First column gives: A080675.
Last elements of rows give: A020522.
Row lengths are: A000081.
Subsequence of A057547, A081292.

Programs

  • Maple
    F:= proc(n) option remember; `if`(n=1, [10], sort(map(h->
          parse(cat(1, sort(h)[], 0)), g(n-1, n-1)))) end:
    g:= proc(n, i) option remember; `if`(i=1, [[10$n]], [seq(seq(seq(
          [seq (F(i)[w[t]-t+1], t=1..j),v[]], w=combinat[choose](
          [$1..nops(F(i))+j-1], j)), v=g(n-i*j, i-1)), j=0..n/i)])
        end:
    b:= proc(n) local h, i, r; h, r:= n, 0; for i from 0
          while h>0 do r:= r+2^i*irem(h, 10, 'h') od; r
        end:
    T:= proc(n) option remember; map(b, F(n))[] end:
    seq(T(n), n=1..7);

Formula

T(n,k) = A216649(n-1,k)*2 + 2^(2*n-1) for n>1.
Showing 1-5 of 5 results.