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 1-2 of 2 results.

A195184 Interspersion fractally induced by the prime marker sequence A089026.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 8, 9, 10, 7, 12, 13, 14, 11, 15, 18, 19, 20, 17, 21, 16, 24, 25, 26, 23, 27, 22, 28, 32, 33, 34, 31, 35, 30, 36, 29, 41, 42, 43, 40, 44, 39, 45, 38, 37, 51, 52, 53, 50, 54, 49, 55, 48, 47, 46, 61, 62, 63, 60, 64, 59, 65, 58, 57, 56, 66, 73, 74, 75
Offset: 1

Views

Author

Clark Kimberling, Sep 10 2011

Keywords

Comments

See A194959 for a discussion of fractalization and the interspersion fractally induced by a sequence. Every pair of rows eventually intersperse. As a sequence, A194184 is a permutation of the positive integers, with inverse A195185. (The prime marker sequence A089026 is given by p(n)=n if n is prime and p(n)=1 otherwise).

Examples

			Northwest corner:
1...2...4...8...12..18..24..32
3...5...9...13..19..26..33..42
6...10..14..20..26..34..43..53
7...11..17..23..31..40..50..60
15..21..27..35..44..54..64..76
		

Crossrefs

Programs

  • Mathematica
    p[n_] := If[PrimeQ[n], n, 1]
    Table[p[n], {n, 1, 90}]  (* A089026 *)
    g[1] = {1}; g[n_] := Insert[g[n - 1], n, p[n]]
    f[1] = g[1]; f[n_] := Join[f[n - 1], g[n]]
    f[20] (* A195183 *)
    row[n_] := Position[f[30], n];
    u = TableForm[Table[row[n], {n, 1, 5}]]
    v[n_, k_] := Part[row[n], k];
    w = Flatten[Table[v[k, n - k + 1], {n, 1, 13}, {k, 1, n}]]  (* A195184 *)
    q[n_] := Position[w, n]; Flatten[Table[q[n], {n, 1, 80}]]  (* A195185 *)

A195185 Inverse permutation of A195184; every positive integer occurs exactly once.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 10, 7, 8, 9, 14, 11, 12, 13, 15, 21, 19, 16, 17, 18, 20, 27, 25, 22, 23, 24, 26, 28, 36, 34, 32, 29, 30, 31, 33, 35, 45, 44, 42, 40, 37, 38, 39, 41, 43, 55, 54, 53, 51, 49, 46, 47, 48, 50, 52, 65, 64, 63, 61, 59, 56, 57, 58, 60, 62, 66, 78, 76, 75
Offset: 1

Views

Author

Clark Kimberling, Sep 10 2011

Keywords

Crossrefs

Programs

  • Mathematica
    p[n_] := If[PrimeQ[n], n, 1]
    Table[p[n], {n, 1, 90}]  (* A089026 *)
    g[1] = {1}; g[n_] := Insert[g[n - 1], n, p[n]]
    f[1] = g[1]; f[n_] := Join[f[n - 1], g[n]]
    f[20] (* A195183 *)
    row[n_] := Position[f[30], n];
    u = TableForm[Table[row[n], {n, 1, 5}]]
    v[n_, k_] := Part[row[n], k];
    w = Flatten[Table[v[k, n - k + 1], {n, 1, 13},
      {k, 1, n}]]  (* A195184 *)
    q[n_] := Position[w, n]; Flatten[
    Table[q[n], {n, 1, 80}]]  (* A195185 *)
Showing 1-2 of 2 results.