A179276 Largest 3-smooth number <= n.

1, 2, 3, 4, 4, 6, 6, 8, 9, 9, 9, 12, 12, 12, 12, 16, 16, 18, 18, 18, 18, 18, 18, 24, 24, 24, 27, 27, 27, 27, 27, 32, 32, 32, 32, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 48, 48, 48, 48, 48, 48, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 64, 64, 64, 64, 64, 64, 64, 64, 72, 72

Offset: 1

Author

Reinhard Zumkeller, Jul 07 2010

Keywords

• nonn
• changed

Links

• David A. Corneth, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A003586, A065331, A065333, A081328, A071521.

Programs

Mathematica

smooth3Q[n_] := FactorInteger[n][[-1, 1]] <= 3;
a[n_] := For[k = n, True, k--, If[smooth3Q[k], Return[k]]];
Table[a[n], {n, 1, 100}] (* Jean-François Alcover, Oct 14 2021 *)

Formula

A065333(a(n)) = 1;

a(A003586(n)) = A003586(n);

A065331(n) <= a(n).

a(n) = A003586(A071521(n)). - Ridouane Oudra, Aug 24 2025

Extensions

Definition corrected by Georg Fischer, Aug 05 2021