cp's OEIS Frontend

A167508 Number of different letters in the French spelling of the number n.

%I A167508 #13 Jun 13 2021 17:09:11
%S A167508 4,2,4,5,6,4,3,4,4,4,3,4,5,5,8,6,4,7,6,7,5,7,9,8,10,7,7,8,7,8,4,5,7,7,
%T A167508 7,7,7,6,7,6,7,7,9,10,7,9,10,9,9,8,8,8,10,11,9,8,10,10,9,9,8,9,10,9,
%U A167508 11,10,8,9,10,10,9,9,11,10,12,11,9,10,11,11,10,10,12,12,10,11,12,12,11,11,12
%N A167508 Number of different letters in the French spelling of the number n.
%C A167508 There is no number which can be written in French using only one letter, therefore the sequence does not contain the term 1.
%C A167508 It appears that letters "j", "k" and "w" don't occur in any number, while "m" and "l" first occur in "mille" (=1000), and "b" first occurs in "billion".
%C A167508 If an "e" with accent (as it occurs in "décillion") is considered as different from "e" without accent, then the range of the sequence should be { 2,3,...,26-3+1 }.
%H A167508 Wiktionnaire, <a href="http://fr.wiktionary.org/wiki/Annexe:Nombres_de_1_%C3%A0_100_en_fran%C3%A7ais">Annexe:Nombres de 1 à 100 en français</a> (as of Nov. 18, 2009).
%e A167508 The terms a(0),...,a(12) represent the number of characters in the strings "zéro", "un", "deux", "trois", "quatre", "cinq", "six", "sept", "huit", "neuf", "dix", "onze", "douze".
%e A167508 Since the "e" occurs twice in "treize", the number of different letters, a(13)=5, is less than the length of this string.
%e A167508 The same is true when the spelling contains hyphens as in "dix-sept" (a(17)=7) or spaces as in "vingt et un" (a(21)=9-2, since among the 9 nonblank characters, "t" and "n" occur twice).
%o A167508 (Python)
%o A167508 import re
%o A167508 from num2words import num2words
%o A167508 from unidecode import unidecode
%o A167508 def A167508(n): return len(set(re.sub("[^a-z]", "", unidecode(num2words(n, lang='fr'))))) # _Chai Wah Wu_, Jun 13 2021
%Y A167508 Cf. A167507.
%K A167508 nonn,word
%O A167508 0,1
%A A167508 _M. F. Hasler_, Nov 18 2009