A330729 Numbers k that are divisible by all integers less than or equal to the cube root of k.

1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 30, 36, 42, 48, 54, 60, 72, 84, 96, 108, 120, 180, 240, 300, 420

Offset

1,2

Links

Table of n, a(n) for n=1..32.

Example

42 appears because the cube root of 42 is approximately 3.48 and 42 is divisible by 3, 2, and 1 (all positive integers less than 3.48).

Mathematica

Select[Range[1000], Divisible[#, LCM @@ Range @ Floor @ Surd[#, 3]] &] (* Amiram Eldar, Dec 28 2019 *)

Prog

(Magma) [k: k in [1..500]|forall{m:m in [1..Floor(k^(1/3))]|k mod m eq 0}]; // Marius A. Burtea, Dec 31 2019
(PARI) is(k) = {my(m=sqrtnint(k, 3)); sum(i=1, m, Mod(k, i)==0) == m; } \\ Jinyuan Wang, Dec 31 2019

Crossrefs

Cf. A003102.

Sequence in context: A080750 A113768 A122936 * A118729 A008726 A302834

Adjacent sequences: A330726 A330727 A330728 * A330730 A330731 A330732

Keyword

nonn,fini,full

Author

Eric Fox, Dec 28 2019

Status

approved