A086297 - OEIS

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A086297

Squarefree kernels of 7-smooth numbers.

1, 2, 3, 2, 5, 6, 7, 2, 3, 10, 6, 14, 15, 2, 6, 10, 21, 6, 5, 3, 14, 30, 2, 35, 6, 10, 42, 15, 6, 7, 10, 6, 14, 30, 21, 2, 70, 6, 15, 10, 3, 42, 30, 6, 14, 10, 105, 6, 14, 30, 5, 42, 2, 15, 70, 6, 21, 30, 10, 6, 42, 35, 30, 21, 6, 14, 10, 210, 6, 14, 15, 30, 3, 35, 10, 42, 2

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OFFSET

1,2

COMMENTS

a(n) = A007947(A002473(n));

a(n) <= 210 = 7*5*3*2; range = A018336.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

MATHEMATICA

f[n_] := If[Max[(p = FactorInteger[n][[;; , 1]])] <= 7, Times @@ p, 0]; Select[f /@ Range[300], # > 0 &] (* Amiram Eldar, Sep 06 2020 *)

CROSSREFS

Cf. A002473, A007947, A018336.