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.

A194878 Rectangular array, by antidiagonals: row n gives the positions of n in the fractal sequence A194877; an interspersion.

Original entry on oeis.org

1, 3, 2, 6, 5, 4, 10, 9, 8, 7, 15, 14, 13, 12, 11, 20, 19, 18, 17, 16, 21, 27, 25, 24, 23, 22, 28, 26, 35, 33, 31, 30, 29, 36, 34, 32, 44, 42, 40, 38, 37, 45, 43, 41, 39, 54, 52, 50, 48, 46, 55, 53, 51, 49, 47, 65, 63, 61, 59, 57, 66, 64, 62, 60, 58, 56, 76, 74, 72
Offset: 1

Views

Author

Clark Kimberling, Sep 04 2011

Keywords

Comments

See A194832 for a general discussion.

Examples

			Northwest corner:
1...3...6...10..15..20..27
2...5...9...14..19..25..33
4...8...13..18..24..31..40
7...12..17..23..30..38..48
11..16..22..29..37..46..57
		

Crossrefs

Programs

  • Mathematica
    r = Sqrt[8];
    t[n_] := Table[FractionalPart[k*r], {k, 1, n}];
    f = Flatten[Table[Flatten[(Position[t[n], #1] &) /@
    Sort[t[n], Less]], {n, 1, 20}]]   (* A194877 *)
    TableForm[Table[Flatten[(Position[t[n], #1] &) /@
    Sort[t[n], Less]], {n, 1, 15}]]
    row[n_] := Position[f, n];
    u = TableForm[Table[row[n], {n, 1, 20}]]
    g[n_, k_] := Part[row[n], k];
    p = Flatten[Table[g[k, n - k + 1], {n, 1, 13},
    {k, 1, n}]]   (* A194878 *)
    q[n_] := Position[p, n]; Flatten[Table[q[n],
    {n, 1, 80}]]   (* A194879 *)