A049528 Number of letters in n-th prime (in English).

3, 5, 4, 5, 6, 8, 9, 8, 11, 10, 9, 11, 8, 10, 10, 10, 9, 8, 10, 10, 12, 11, 11, 10, 11, 13, 15, 15, 14, 18, 21, 19, 21, 20, 19, 18, 20, 20, 20, 22, 21, 19, 19, 21, 21, 20, 16, 21, 21, 20, 21, 20, 18, 18, 20, 20, 19, 20, 22, 19, 21, 21, 17, 18, 20, 21, 21, 23

Offset: 1

Author

G. L. Honaker, Jr.

Keywords

• easy
• nice
• nonn
• word

Examples

			a(13) = 8 because 'forty-one' contains 8 letters (not counting the hyphen).
		

Links

• Michael S. Branicky, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A005589, A052360.

Programs

Python

from sympy import nextprime
from itertools import count, islice
from num2words import num2words as n2w
def f(n): return sum(1 for c in n2w(n).replace(" and", "") if c.isalpha())
def agen(p=2):
    while True: yield f(p); p = nextprime(p)
print(list(islice(agen(), 68))) # Michael S. Branicky, Jul 12 2022

Formula

a(n) = A005589(A000040(n)) or a(n) = A052360(A000040(n)) depending on whether hyphens and spaces are excluded or included. - Jonathan Vos Post, Oct 19 2007

a(n) = A005589(A000040(n)) since it does not count spaces or hyphens. - Michael S. Branicky, Jul 12 2022

Extensions

a(66) and beyond from Michael S. Branicky, Jul 12 2022