

A072687


Number of primes with prime length names in range 1 > 10^n.


2




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

Table of n, a(n) for n=1..9.
Sean A. Irvine, Java program (github)


EXAMPLE

E.g., from the sequence of the valid primes (A072686) there are three primelength 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

Cf. A072686.
Sequence in context: A180368 A108262 A034892 * A260817 A262126 A110561
Adjacent sequences: A072684 A072685 A072686 * A072688 A072689 A072690


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



