cp's OEIS Frontend

A161140 Numbers which can be expressed as the product of numbers made of only twos.

%I A161140 #12 Dec 05 2024 18:59:07
%S A161140 1,2,4,8,16,22,32,44,64,88,128,176,222,256,352,444,484,512,704,888,
%T A161140 968,1024,1408,1776,1936,2048,2222,2816,3552,3872,4096,4444,4884,5632,
%U A161140 7104,7744,8192,8888,9768,10648,11264,14208,15488,16384,17776
%N A161140 Numbers which can be expressed as the product of numbers made of only twos.
%H A161140 Robert Israel, <a href="/A161140/b161140.txt">Table of n, a(n) for n = 1..10000</a>
%e A161140 1 is the empty product; 44 is in the list because 44 = 2 * 22, 484 is in the list because 484 = 22 * 22.
%p A161140 M:= 10^8:
%p A161140 S:= {1}:
%p A161140 for d from 1 to ilog10(M) do
%p A161140   x:= 2/9*(10^d-1); T:= {}:
%p A161140   for s in S do
%p A161140     T:= T union {seq(s*x^i,i=1..floor(log[x](M/s)))};
%p A161140   od;
%p A161140   S:= S union T;
%p A161140 od:
%p A161140 sort(convert(S,list)); # _Robert Israel_, Dec 05 2024
%Y A161140 Cf. A084034, A161141, A161142, A161143, A161144, A161145, A161146, A161147.
%K A161140 nonn,base
%O A161140 1,2
%A A161140 _Claudio Meller_, Jun 03 2009
%E A161140 1 added by _N. J. A. Sloane_, Dec 04 2017