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Numbers containing all divisors in their binary representation.
5

%I #17 Jun 05 2022 08:31:15

%S 1,2,3,4,5,6,7,8,10,11,12,13,14,16,17,19,20,22,23,24,26,28,29,31,32,

%T 34,37,38,40,41,43,44,46,47,48,52,53,55,56,58,59,61,62,64,67,68,71,73,

%U 74,76,79,80,82,83,86,88,89,92,94,96,97,101,103,104,106,107,109,112,113,116,118

%N Numbers containing all divisors in their binary representation.

%H Reinhard Zumkeller, <a href="/A123345/b123345.txt">Table of n, a(n) for n = 1..10000</a>

%t q[n_] := AllTrue[Divisors[n], StringContainsQ[IntegerString[n, 2], IntegerString[#, 2]] &]; Select[Range[100], q] (* _Amiram Eldar_, Jun 05 2022 *)

%o (Haskell)

%o import Data.List (unfoldr, isInfixOf)

%o a123345 n = a123345_list !! (n-1)

%o a123345_list = filter

%o (\x -> all (`isInfixOf` b x) $ map b $ a027750_row x) [1..] where

%o b = unfoldr (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 2)

%o -- _Reinhard Zumkeller_, Oct 27 2012

%o (Python)

%o from sympy import divisors

%o def ok(n):

%o b = bin(n)[2:]

%o return n and all(bin(d)[2:] in b for d in divisors(n, generator=True))

%o print([k for k in range(119) if ok(k)]) # _Michael S. Branicky_, Jun 05 2022

%Y Complement of A093642. Different from A093641.

%Y Cf. A000040 (subsequence), A027750, A218388.

%K nonn,base

%O 1,2

%A _Reinhard Zumkeller_, Oct 12 2006