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.

A191545 Dispersion of (floor(9*n/4)), by antidiagonals.

Original entry on oeis.org

1, 2, 3, 4, 6, 5, 9, 13, 11, 7, 20, 29, 24, 15, 8, 45, 65, 54, 33, 18, 10, 101, 146, 121, 74, 40, 22, 12, 227, 328, 272, 166, 90, 49, 27, 14, 510, 738, 612, 373, 202, 110, 60, 31, 16, 1147, 1660, 1377, 839, 454, 247, 135, 69, 36, 17, 2580, 3735, 3098, 1887
Offset: 1

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Author

Clark Kimberling, Jun 09 2011

Keywords

Comments

Background discussion: Suppose that s is an increasing sequence of positive integers, that the complement t of s is infinite, and that t(1)=1. The dispersion of s is the array D whose n-th row is (t(n), s(t(n)), s(s(t(n))), s(s(s(t(n)))), ...). Every positive integer occurs exactly once in D, so that, as a sequence, D is a permutation of the positive integers. The sequence u given by u(n)=(number of the row of D that contains n) is a fractal sequence. Examples:
(1) s=A000040 (the primes), D=A114537, u=A114538.
(2) s=A022343 (without initial 0), D=A035513 (Wythoff array), u=A003603.
(3) s=A007067, D=A035506 (Stolarsky array), u=A133299.
More recent examples of dispersions: A191426-A191455.

Examples

			Northwest corner:
  1   2    4    9    20
  3   6    13   29   65
  5   11   25   54   121
  7   15   33   74   166
  8   18   40   90   202
		

Crossrefs

Programs

  • Mathematica
    (* Program generates the dispersion array T of the complement of increasing sequence f[n] *)
    r=40; r1=12; c=40; c1=12; f[n_] := Floor[9n/4]   (* complement of column 1 *)
    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}];
    t[i_, j_] := rows[[i, j]];
    TableForm[Table[t[i, j], {i, 1, 10}, {j, 1, 10}]]
    (* A191545 array *)
    Flatten[Table[t[k, n - k + 1], {n, 1, c1}, {k, 1, n}]] (* A191545 sequence *)
    (* Program by Peter J. C. Moses, Jun 01 2011 *)