A225985 - OEIS

%I #26 Aug 06 2022 08:23:12

%S 1,3,5,7,9,1,11,1,13,1,15,1,17,1,19,1,3,5,7,9,3,31,3,33,3,35,3,37,3,

%T 39,1,3,5,7,9,5,51,5,53,5,55,5,57,5,59,1,3,5,7,9,7,71,7,73,7,75,7,77,

%U 7,79,1,3,5,7,9,9,91,9,93,9,95,9,97,9,99,1,11,1,13

%N List the positive numbers, remove even digits (including zeros) from each term; sequence = remaining terms.

%H Paul Tek, <a href="/A225985/b225985.txt">Table of n, a(n) for n = 1..10000</a>

%F a(A226091(n)) = A014261(n). - _Reinhard Zumkeller_, May 26 2013

%e The natural numbers with at least one odd digit in their decimal representation are: 1, 3, 5, 7, 9, 10, 11, 12, 13, ...

%e By excluding their even digits, we obtain: 1, 3, 5, 7, 9, 1, 11, 1, 13, ...

%e Hence: a(1)=1, a(2)=3, a(3)=5, a(4)=7, a(5)=9, a(6)=1, a(7)=11, a(8)=1, a(9)=13, .... [Example corrected by _Paul Tek_, May 24 2013]

%t FromDigits[DeleteCases[IntegerDigits[#],_?EvenQ]]&/@Range[200]/. (0-> Nothing) (* _Harvey P. Dale_, Apr 04 2017 *)

%o (Haskell)

%o a225985 n = a225985_list !! (n-1)

%o a225985_list = map read $ filter (not . null) $

%o     map (filter (`elem` "13579") . show) [0..] :: [Integer]

%o -- _Reinhard Zumkeller_, May 26 2013

%o (Python)

%o from itertools import count, islice

%o def agen(): # generator of terms

%o     for n in count(1):

%o         removed  = "".join(d if d in "13579" else "" for d in str(n))

%o         if removed != "": yield int(removed)

%o print(list(islice(agen(), 80))) # _Michael S. Branicky_, Aug 05 2022

%Y Cf. A038573.

%Y Cf. A014261 (duplicates removed), A226091.

%K nonn,base,look

%O 1,2

%A _Dave Durgin_, May 22 2013

%E Definition clarified by _N. J. A. Sloane_, Aug 06 2022 at the suggestion of _Michel Marcus_