A008521 - OEIS

%I #24 Feb 16 2025 08:32:32

%S 3,5,6,7,8,9,10,11,12,13,15,16,17,18,19,20,23,25,26,27,28,29,30,33,35,

%T 36,37,38,39,50,53,55,56,57,58,59,60,63,65,66,67,68,69,70,73,75,76,77,

%U 78,79,80,83,85,86,87,88,89,90,93,95,96,97,98,99,300,303,305,306,307

%N Numbers that do not contain the letter 'o'.

%C There are exactly 454 oban numbers. - _Eric W. Weisstein_, Nov 09 2003

%H Reinhard Zumkeller, <a href="/A008521/b008521.txt">Table of n, a(n) for n = 1..454</a>

%H Roel and Bas van Dijk, <a href="http://hackage.haskell.org/package/numerals">Numerals package</a>, Hackage (Haskell packages).

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ObanNumber.html">Oban Number</a>

%H <a href="/index/Lc#letters">Index entries for sequences related to number of letters in n</a>

%o (Haskell)

%o import Data.Maybe (fromJust)

%o import Data.Text (Text); import qualified Data.Text as T (all)

%o import Text.Numeral.Grammar.Reified (defaultInflection)

%o import qualified Text.Numeral.Language.EN as EN  -- see link

%o a008521 n = a008521_list !! (n-1)

%o a008521_list = filter (T.all (/= 'o') . numeral) [0..] where

%o    numeral :: Integer -> Text

%o    numeral = fromJust . EN.gb_cardinal defaultInflection

%o -- _Reinhard Zumkeller_, Jan 23 2015

%o (Python)

%o from num2words import num2words

%o afull = [k for k in range(1000) if "o" not in num2words(k)]

%o print(afull[:70]) # _Michael S. Branicky_, Aug 18 2022

%Y Cf. A006933 (ban e), A089589 (ban i), A008523 (ban t), A089590 (ban u).

%K nonn,word,fini,full

%O 1,1

%A _N. J. A. Sloane_