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

0,1

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 }.

Links

Table of n, a(n) for n=0..90.

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

Example

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).

Prog

(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

Crossrefs

Cf. A167507.

Sequence in context: A021706 A224183 A131953 * A167507 A007005 A237869

Adjacent sequences: A167505 A167506 A167507 * A167509 A167510 A167511

Keyword

nonn,word

Author

M. F. Hasler, Nov 18 2009

Status

approved