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A161142
Numbers which can be expressed as the product of numbers made of only fours.
8
1, 4, 16, 44, 64, 176, 256, 444, 704, 1024, 1776, 1936, 2816, 4096, 4444, 7104, 7744, 11264, 16384, 17776, 19536, 28416, 30976, 44444, 45056, 65536, 71104, 78144, 85184, 113664, 123904, 177776, 180224, 195536, 197136, 262144, 284416, 312576
OFFSET
1,2
COMMENTS
64 = 4 * 4 * 4; 1936 = 44 * 44; 1776 = 4 * 444.
LINKS
MAPLE
M:= 10^6: # for terms <= M
S:= {1}:
for d from 1 to ilog10(M) do
x:= 4/9*(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
KEYWORD
nonn,base
AUTHOR
Claudio Meller, Jun 03 2009
EXTENSIONS
Corrected and extended by Claudio Meller, Jun 06 2009
Corrected and extended by Claudio Meller, Jun 27 2009
1 added by N. J. A. Sloane, Dec 04 2017
STATUS
approved