A225985 List the positive numbers, remove even digits (including zeros) from each term; sequence = remaining terms.

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

Offset: 1

Author

Dave Durgin, May 22 2013

Keywords

• nonn
• base
• look

Examples

			The natural numbers with at least one odd digit in their decimal representation are: 1, 3, 5, 7, 9, 10, 11, 12, 13, ...
By excluding their even digits, we obtain: 1, 3, 5, 7, 9, 1, 11, 1, 13, ...
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]
		

Links

• Paul Tek, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A038573.

Cf. A014261 (duplicates removed), A226091.

Programs

Haskell

a225985 n = a225985_list !! (n-1)
a225985_list = map read $ filter (not . null) $
    map (filter (`elem` "13579") . show) [0..] :: [Integer]
-- Reinhard Zumkeller, May 26 2013

Mathematica

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

Python

from itertools import count, islice
def agen(): # generator of terms
    for n in count(1):
        removed  = "".join(d if d in "13579" else "" for d in str(n))
        if removed != "": yield int(removed)
print(list(islice(agen(), 80))) # Michael S. Branicky, Aug 05 2022

Formula

a(A226091(n)) = A014261(n). - Reinhard Zumkeller, May 26 2013

Extensions

Definition clarified by N. J. A. Sloane, Aug 06 2022 at the suggestion of Michel Marcus