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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A207384 A206815(n+1)-A206815(n).

Original entry on oeis.org

1, 3, 2, 2, 2, 3, 1, 2, 2, 3, 1, 3, 2, 2, 1, 3, 2, 3, 1, 2, 2, 3, 2, 1, 2, 2, 2, 2, 2, 3, 2, 2, 1, 2, 2, 3, 2, 1, 2, 3, 2, 2, 2, 2, 2, 3, 2, 1, 2, 2, 2, 3, 1, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 1, 2, 3, 2, 2, 1, 3, 2, 3, 2, 1, 2, 2, 2, 3, 2, 1, 2, 3, 2, 2, 1, 2, 2, 3, 2, 2, 1, 2, 2, 2, 2, 3, 1, 2, 2
Offset: 1

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Author

Clark Kimberling, Feb 17 2012

Keywords

Comments

The sequences A206815, A206818, A207384, A207835 illustrate the closeness of {j+pi(j)} to {k+(k+1)/log(k+1)}, as suggested by the prime number theorem and the conjecture that all the terms of A207384 and A207835 are in the set {1,2,3}.

Examples

			The joint ranking is represented by
1 < 3 < 3.8 < 4.7 < 5 < 5.8 < 6 <7.1 < 8 < 8.3 < 9 < ...
Positions of numbers j+pi(j): 1,2,5,7,9,...
Positions of numbers k+(k+1)/log(k+1): 3,4,6,8,10,..
		

Crossrefs

Programs

  • Mathematica
    f[1, n_] := n + PrimePi[n];
    f[2, n_] := n + N[(n + 1)/Log[n + 1]]; z = 500;
    t[k_] := Table[f[k, n], {n, 1, z}];
    t = Sort[Union[t[1], t[2]]];
    p[k_, n_] := Position[t, f[k, n]];
    Flatten[Table[p[1, n], {n, 1, z}]]    (* A206815 *)
    Flatten[Table[p[2, n], {n, 1, z}]]    (* A206818 *)
    d1[n_] := p[1, n + 1] - p[1, n]
    Flatten[Table[d1[n], {n, 1, z - 1}]]  (* A207385 *)
    d2[n_] := p[2, n + 1] - p[2, n]
    Flatten[Table[d2[n], {n, 1, z - 1}]]  (* A207386 *)
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