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A113458 Least k such that k, k+n and k+2n have the same prime signature. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Third row of A113456.
LINKS
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
Sequence in context: A135088 A346496 A113467 * A120584 A236177 A123173
KEYWORD
easy,nonn
AUTHOR
David Wasserman, Jan 08 2006
STATUS
approved

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Last modified March 28 15:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)