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

Offset: 1

Author

Reinhard Zumkeller, Jul 15 2003

Keywords

• nonn

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

Crossrefs

Cf. A002473, A007947, A018336.

Programs

Mathematica

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