A110789 Number of digits in A110788(n).

1, 1, 2, 4, 5, 10, 23, 102, 102, 138, 451, 1922, 1624, 5630, 26410

Offset: 1

Author

Amarnath Murthy, Aug 13 2005

Keywords

• base
• nonn
• more

Crossrefs

Cf. A110774, A110775, A110776, A110777, A110778, A110780, A110781, A110782, A110783, A110788.

Programs

Python

from sympy import isprime
from itertools import count, islice
def agen(): # generator of terms
    s = ""
    while True:
        for d in "71":
            for k in count(1):
                if isprime(int(s+d*k)): break
            yield k
            s += d*k
print(list(islice(agen(), 11))) # Michael S. Branicky, Aug 23 2022

Extensions

More terms from Joshua Zucker, Jan 11 2006

a(12) from Sean A. Irvine, Mar 22 2010

a(13)-a(14) from Michael S. Branicky, Aug 23 2022

a(15) from Michael S. Branicky, Nov 20 2024