A113458 Least k such that k, k+n and k+2n have the same prime signature.

33, 3, 155, 3, 77, 5, 51, 3, 77, 3, 35, 5, 50, 3, 187, 6, 21, 5, 39, 3, 145, 33, 39, 5, 69, 39, 91, 3, 33, 7, 15, 12, 221, 3, 28, 7, 21, 3, 55, 3, 33, 5, 91, 66, 209, 69, 35, 5, 50, 3, 115, 39, 141, 5, 51, 6, 145, 85, 15, 7, 21, 93, 95, 3, 57, 5, 51, 3, 65, 15, 35, 7, 69, 55, 287, 6

Offset

1,1

Comments

Third row of A113456.

Links

Alois P. Heinz, Table of n, a(n) for n = 1..20000

Example

a(4) = 3 because 3, 7 and 11 have the same prime signature.

Maple

s:= n-> sort(map(i-> i[2], ifactors(n)[2])):
a:= proc(n) option remember; local k; for k
      while s(k)<>s(k+n) or s(k)<>s(k+2*n) do od; k
    end:
seq(a(n), n=1..100);  # Alois P. Heinz, Feb 28 2018

Mathematica

s[n_] := FactorInteger[n][[All, 2]] // Sort;
a[n_] := Module[{k}, For[k = 2, True, k++, If[s[k] == s[k+n] == s[k+2n], Return[k]]]];
Array[a, 100] (* Jean-François Alcover, Nov 05 2020 *)

Crossrefs

Cf. A052214, A113456, A113467.

Sequence in context: A135088 A346496 A113467 * A120584 A236177 A123173

Adjacent sequences: A113455 A113456 A113457 * A113459 A113460 A113461

Keyword

easy,nonn

Author

David Wasserman, Jan 08 2006

Status

approved