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.

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A087469 a(n) = number of the row (counting from initial row 0) of the array R in A087468 that contains n.

Original entry on oeis.org

0, 1, 0, 2, 1, 3, 0, 2, 4, 1, 3, 0, 5, 2, 4, 1, 6, 3, 0, 5, 2, 7, 4, 1, 6, 3, 0, 8, 5, 2, 7, 4, 1, 9, 6, 3, 0, 8, 5, 2, 10, 7, 4, 1, 9, 6, 3, 0, 11, 8, 5, 2, 10, 7, 4, 1, 12, 9, 6, 3, 0, 11, 8, 5, 2, 13, 10, 7, 4, 1, 12, 9, 6, 3, 0, 14, 11, 8, 5, 2, 13, 10, 7, 4, 1, 15, 12, 9, 6, 3, 0, 14, 11, 8, 5, 2, 16
Offset: 1

Views

Author

Clark Kimberling, Sep 09 2003

Keywords

Comments

A fractal sequence.

Examples

			Northwest corner of R:
.1 3 7 12 19
.2 5 10 16 24
.4 8 14 21 30
.6 11 18 26 36
.9 15 23 32 43
a(11)=3 because 11 is in row 3.
		

Crossrefs

A087470 a(n) = number of the row (counting from initial row 1) of the array R in A087468 that contains n.

Original entry on oeis.org

1, 2, 1, 3, 2, 4, 1, 3, 5, 2, 4, 1, 6, 3, 5, 2, 7, 4, 1, 6, 3, 8, 5, 2, 7, 4, 1, 9, 6, 3, 8, 5, 2, 10, 7, 4, 1, 9, 6, 3, 11, 8, 5, 2, 10, 7, 4, 1, 12, 9, 6, 3, 11, 8, 5, 2, 13, 10, 7, 4, 1, 12, 9, 6, 3, 14, 11, 8, 5, 2, 13, 10, 7, 4, 1, 15, 12, 9, 6, 3, 14, 11, 8, 5, 2, 16, 13, 10, 7, 4, 1, 15, 12, 9, 6
Offset: 1

Views

Author

Clark Kimberling, Sep 09 2003

Keywords

Comments

A fractal sequence.

Examples

			Northwest corner of R:
1 3 7 12 19
2 5 10 16 24
4 8 14 21 30
6 11 18 26 36
9 15 23 32 43
a(11)=4 because 11 is in row 4.
		

Crossrefs

A087465 Rank array R of 3/2 read by antidiagonals; this array is the dispersion of the complement of the sequence given by r(n) = r(n-1) + 1 + floor(3n/2) for n>=1, with r(0) = 1; that is, A077043(n+1).

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 6, 8, 10, 12, 9, 11, 14, 16, 19, 13, 15, 18, 21, 24, 27, 17, 20, 23, 26, 30, 33, 37, 22, 25, 29, 32, 36, 40, 44, 48, 28, 31, 35, 39, 43, 47, 52, 56, 61, 34, 38, 42, 46, 51, 55, 60, 65, 70, 75, 41, 45, 50, 54, 59, 64, 69, 74, 80, 85, 91, 49, 53, 58, 63, 68, 73
Offset: 0

Views

Author

Clark Kimberling, Sep 09 2003

Keywords

Comments

The sequence is a permutation of the positive integers and the array is a transposable dispersion.
Let T(n,k) be the rectangular version of the array at A036561, with northwest corner as shown here:
1 2 4 8 16 32
3 6 12 24 48 96
9 18 36 72 144 288
27 54 108 216 432 864
Then R(n,k) is the rank of T(n,k) when all the numbers in {T(n,k)} are jointly ranked. - Clark Kimberling, Jan 25 2018

Examples

			Northwest corner of R:
   1    2    4    6    9   13   17   22
   3    5    8   11   15   20   25   31
   7   10   14   18   23   29   35   42
  12   16   21   26   32   39   46   54
  19   24   30   36   43   51   59   68
  27   33   40   47   55   64   73   83
  37   44   52   60   69   79   89  100
Let t=3/2; then R(i,j) = rank of (j,i) when all nonnegative integer pairs (a,b) are ranked by the relation << defined as follows: (a,b) << (c,d) if a + b*t < c + d*t, and also (a,b) << (c,d) if a + b*t = c + d*t and b < d.  Thus R(2,1) = 10 is the rank of (1,2) in the list (0,0) << (1,0) << (0,1) << (2,0) << (1,1) << (3,0) << (0,2) << (2,1) << (4,0) << (1,2).
		

Crossrefs

Cf. A087466, A087468, A087483, A007780 (row 1), A077043 (column 1).

Programs

  • Mathematica
    r = 20; r1 = 12;(*r=# rows of T,r1=# rows to show*);
    c = 20; c1 = 12;(*c=# cols of T,c1=# cols to show*);
    s[0] = 1; s[n_] := s[n] = s[n - 1] + 1 + Floor[3 n/2]; u = Table[s[n], {n, 0, 100}]
    v = Complement[Range[Max[u]], u]; f[n_] := v[[n]]; Table[f[n], {n, 1, 30}]
    mex[list_] := NestWhile[#1 + 1 &, 1, Union[list][[#1]] <= #1 &, 1,   Length[Union[list]]]; rows = {NestList[f, 1, c]}; Do[rows = Append[rows, NestList[f, mex[Flatten[rows]], r]], {r}]; w[i_, j_] := rows[[i, j]];
    TableForm[Table[w[i, j], {i, 1, 10}, {j, 1, 10}]]   (* A087465 array *)
    Flatten[Table[w[k, n - k + 1], {n, 1, c1}, {k, 1, n}]] (* A087465 sequence *)
    TableForm[Table[w[i, 1] + w[1, j] + (i - 1)*(j - 1) - 1, {i, 1, 10}, {j, 1, 10}]] (* A087465 array, by formula *)

Formula

R(i,j) = R(i,0) + R(0,j) + i*j - 1, for i>=1, j>=1.

Extensions

Updated by Clark Kimberling, Sep 23 2014

A087483 Row 0 of the order array of 3/2, i.e., row 0 of the transposable dispersion in A087465.

Original entry on oeis.org

1, 2, 4, 6, 9, 13, 17, 22, 28, 34, 41, 49, 57, 66, 76, 86, 97, 109, 121, 134, 148, 162, 177, 193, 209, 226, 244, 262, 281, 301, 321, 342, 364, 386, 409, 433, 457, 482, 508, 534, 561, 589, 617, 646, 676, 706, 737, 769, 801, 834, 868, 902, 937, 973, 1009, 1046, 1084
Offset: 0

Views

Author

Clark Kimberling, Sep 09 2003

Keywords

Comments

Also, column 0 of the transposable dispersion in A087468.

Crossrefs

Programs

Formula

a(n) = n + 1 - floor(n/3) + Sum_{i=1..n} floor(2i/3).
a(n) = 1 + floor((n+1)^2/3) = 1 + A000212(n+1).
a(n) = A192735(n+2) / (n+2). - Reinhard Zumkeller, Jul 08 2011
G.f.: -(x^4-x^3+x^2+1) / ((x-1)^3*(x^2+x+1)). - Colin Barker, Mar 31 2013

Extensions

Edited by Max Alekseyev, Dec 05 2013
Showing 1-4 of 4 results.