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.

A248513 Rectangular array by antidiagonals: the dispersion of A181155 ("odious numbers").

Original entry on oeis.org

1, 2, 4, 3, 8, 6, 5, 15, 12, 7, 9, 29, 23, 14, 10, 17, 57, 45, 27, 20, 11, 33, 113, 89, 53, 39, 22, 13, 65, 225, 177, 105, 77, 43, 26, 16, 129, 449, 353, 209, 153, 85, 51, 32, 18, 257, 897, 705, 417, 305, 169, 101, 63, 36, 19, 513, 1793, 1409, 833, 609, 337
Offset: 1

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Author

Clark Kimberling, Oct 08 2014

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, as in A248514.
The n-th term of column 1 is A001969(n) + 1, where A001969 are the "evil numbers".

Examples

			Northwest corner:
  1 ... 2 ... 3 ... 5 ... 9 .... 17 ... 33
  4 ... 8 ... 15 .. 29 .. 57 ... 113 .. 225
  6 ... 12 .. 23 .. 45 .. 89 ... 177 .. 353
  7 ... 14 .. 27 .. 53 .. 105 .. 209 .. 417
  10 .. 20 .. 39 .. 77 .. 153 .. 305 .. 609
		

References

  • Clark Kimberling, Fractal sequences and interspersions, Ars Combinatoria 45 (1997) 157-168.

Crossrefs

Cf. A248514.

Programs

  • Mathematica
    r = 40; r1 = 10; (* r = # rows of T, r1 = # rows to show *);
    c = 40; c1 = 12; (* c = # cols of T, c1 = # cols to show *);
    x = GoldenRatio;
    s[n_] := s[n] = If[n < 1, 0, 2 n - Mod[Total[IntegerDigits[n - 1, 2]], 2]];
    mex[list_] := NestWhile[#1 + 1 &, 1, Union[list][[#1]] <= #1 &, 1,   Length[Union[list]]]; rows = {NestList[s, 1, c]};
    Do[rows = Append[rows, NestList[s, mex[Flatten[rows]], r]], {r}];
    t[i_, j_] := rows[[i, j]]; TableForm[Table[t[i, j], {i, 1, r1}, {j, 1, c1}]]
    u = Flatten[Table[t[k, n - k + 1], {n, 1, c1}, {k, 1, n}]] (* A248513 *)
    row[i_] := row[i] = Table[t[i, j], {j, 1, c}]
    f[n_] := Select[Range[r], MemberQ[row[#], n] &]
    v = Flatten[Table[f[n], {n, 1, 200}]]  (* A248514 *)