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

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, 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, 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

Offset: 0

Author

M. F. Hasler, Nov 18 2009

Keywords

• nonn
• word

Comments

There is no number which can be written in French using only one letter, therefore the sequence does not contain the term 1.

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".

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 }.

Examples

			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".
Since the "e" occurs twice in "treize", the number of different letters, a(13)=5, is less than the length of this string.
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).
		

Links

• Wiktionnaire, Annexe:Nombres de 1 à 100 en français (as of Nov. 18, 2009).

Crossrefs

Cf. A167507.

Programs

Python

import re
from num2words import num2words
from unidecode import unidecode
def A167508(n): return len(set(re.sub("[^a-z]", "", unidecode(num2words(n, lang='fr'))))) # Chai Wah Wu, Jun 13 2021