A128530 Nontrivial products of three lucky numbers.

27, 63, 81, 117, 135, 147, 189, 225, 243, 273, 279, 297, 315, 333, 343, 351, 387, 405, 441, 459, 507, 525, 567, 585, 603, 621, 637, 651, 657, 675, 693, 711, 729, 735, 777, 783, 819, 837, 891, 903, 945, 975, 999, 1029, 1035, 1053, 1071, 1125, 1143, 1161, 1183

Offset

1,1

Comments

This is to lucky numbers (A000959) greater than 1 as A014612 (numbers that are divisible by exactly 3 primes, counted with multiplicity) are to primes. This is to 3 as A128462 (Nontrivial products of two lucky numbers) is to 2.

Links

Table of n, a(n) for n=1..51.

Formula

{A000959(i)*A000959(j)*A000959(k) for i, j, k > 1}.

Mathematica

Lc = {3, 7, 9, 13, 15, 21, 25, 31, 33, 37, 43, 49, 51, 63, 67, 69, 73, 75, 79, 87, 93, 99, 105, 111, 115, 127, 129}; Select[Union[Times @@@ Tuples[{Lc, Lc, Lc}]], # <= 9 Max[Lc] &] (* Giovanni Resta, Jun 19 2016 *)

Crossrefs

Cf. A000959, A001358, A128462.

Sequence in context: A180574 A107580 A138610 * A044129 A044510 A338556

Adjacent sequences: A128527 A128528 A128529 * A128531 A128532 A128533

Keyword

easy,nonn

Author

Jonathan Vos Post, May 07 2007

Extensions

Data corrected by Giovanni Resta, Jun 19 2016

Status

approved