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A028846 Numbers whose product of digits is a power of 2. 17
1, 2, 4, 8, 11, 12, 14, 18, 21, 22, 24, 28, 41, 42, 44, 48, 81, 82, 84, 88, 111, 112, 114, 118, 121, 122, 124, 128, 141, 142, 144, 148, 181, 182, 184, 188, 211, 212, 214, 218, 221, 222, 224, 228, 241, 242, 244, 248, 281, 282, 284, 288, 411, 412, 414, 418, 421, 422, 424, 428, 441, 442, 444, 448 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Numbers using only digits 1, 2, 4, and 8. - Michel Lagneau, Dec 01 2010
LINKS
FORMULA
Given a(0) = 0 and n = 4k - r, where 0 <= r <= 3, a(n) = 10*a(k-1) + 2^(3-r). - Clinton H. Dan, Aug 21 2022
EXAMPLE
28 is in the sequence because 2*8 = 2^4. - Michel Lagneau, Dec 01 2010
MATHEMATICA
Select[Range[1000], IntegerQ[Log[2, Times @@ (IntegerDigits[#])]] &] (* Michel Lagneau, Dec 01 2010 *)
PROG
(Haskell)
a028846 n = a028846_list !! (n-1)
a028846_list = f [1] where
f ds = foldr (\d v -> 10 * v + d) 0 ds : f (s ds)
s [] = [1]; s (8:ds) = 1 : s ds; s (d:ds) = 2*d : ds
-- Reinhard Zumkeller, Jan 13 2014
(Python)
from itertools import count, islice, product
def agen(): yield from (int("".join(p)) for d in count(1) for p in product("1248", repeat=d))
print(list(islice(agen(), 64))) # Michael S. Branicky, Aug 21 2022
CROSSREFS
Sequence in context: A028889 A235700 A174781 * A274924 A080152 A136994
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu)
STATUS
approved

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Last modified March 28 10:31 EDT 2024. Contains 371240 sequences. (Running on oeis4.)