OFFSET
1,1
COMMENTS
This sequence uses "and" (e.g., "one hundred and one") and does not count spaces, commas, or hyphens. - Michael S. Branicky, Mar 08 2021
LINKS
Sean A. Irvine, Java program (github)
EXAMPLE
E.g., from the sequence of the valid primes (A072686) there are three prime-length primes between 1 and 10: 2,3,7; therefore a(1)=3.
23 ("twentythree", 11 letters) and 109 ("one hundred and nine", 17 letters) are counted.
PROG
(Python)
from num2words import num2words
from sympy import isprime, primerange
def n2w(n):
return num2words(n).replace(", ", "").replace(" ", "").replace("-", "")
def a(n): return sum(isprime(len(n2w(p))) for p in primerange(2, 10**n))
print([a(n) for n in range(1, 7)]) # Michael S. Branicky, Mar 08 2021
CROSSREFS
KEYWORD
more,nonn,word
AUTHOR
Mark Hudson (mrmarkhudson(AT)hotmail.com), Jul 02 2002
EXTENSIONS
a(6)-a(8) from Sean A. Irvine, Nov 08 2011
a(8) corrected by Sean A. Irvine, Apr 28 2019
a(8) corrected and a(9) from Michael S. Branicky, Mar 08 2021
STATUS
approved