A161141 Numbers which can be expressed as the product of numbers made of only threes.

1, 3, 9, 27, 33, 81, 99, 243, 297, 333, 729, 891, 999, 1089, 2187, 2673, 2997, 3267, 3333, 6561, 8019, 8991, 9801, 9999, 10989, 19683, 24057, 26973, 29403, 29997, 32967, 33333, 35937, 59049, 72171, 80919, 88209, 89991, 98901, 99999, 107811

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

1 = empty product; 99 = 3 * 33; 1089 = 33 * 33; 999 = 3 * 333.

Maple

M:= 10^8: # for terms <= M
S:= {1}:
for d from 1 to ilog10(M) do
  x:= 3/9*(10^d-1); T:= {}:
  for s in S do
    T:= T union {seq(s*x^i, i=1..floor(log[x](M/s)))};
  od;
  S:= S union T;
od:
sort(convert(S, list)); # Robert Israel, Dec 05 2024

Crossrefs

Cf. A084034, A161140, A161142, A161143, A161144, A161145, A161146, A161147.

Sequence in context: A029454 A095309 A191126 * A057238 A070364 A070363

Adjacent sequences: A161138 A161139 A161140 * A161142 A161143 A161144

Keyword

nonn,base

Author

Claudio Meller, Jun 03 2009

Extensions

Corrected and extended by Claudio Meller, Jun 06 2009

1 added by N. J. A. Sloane, Dec 04 2017

Status

approved