A118643 Lucky numbers whose prime factors are also lucky numbers.

1, 3, 7, 9, 13, 21, 31, 37, 43, 49, 63, 67, 73, 79, 93, 111, 127, 129, 151, 163, 169, 189, 193, 201, 211, 219, 223, 237, 241, 259, 273, 283, 307, 331, 349, 367, 409, 421, 433, 463, 487, 489, 511, 541, 553, 559, 577, 579, 601, 613, 619, 631, 643, 651, 673, 723

Offset

1,2

Links

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

Example

189 is included since 189 is lucky and 189 = 3*3*3*7 has prime factors that are all lucky.

Mathematica

L = Table[2*i + 1, {i, 0, 362}]; For[n = 2, n < Length[L], r = L[[n++]]; L = ReplacePart[L, Table[r*i -> Nothing, {i, 1, Length[L]/r}]]]; Select[L, ContainsOnly[First/@FactorInteger[#], L]&] (* James C. McMahon, Sep 19 2024 *)

Crossrefs

Cf. A000959, (lucky numbers), A043772 (superset).

Sequence in context: A291344 A297002 A111250 * A043772 A176553 A109370

Adjacent sequences: A118640 A118641 A118642 * A118644 A118645 A118646

Keyword

easy,nonn

Author

Adam Panagos (adam.panagos(AT)gmail.com), May 10 2006

Status

approved