A108847 Palindromic primes in which all internal digits are 8.

181, 383, 787, 78887, 9888889, 188888881, 3888888888883, 188888888888881, 3888888888888888888888888888883, 18888888888888888888888888888888888888881

Offset

1,1

Comments

a(27) has 1065 digits. - Michael S. Branicky, Jan 27 2023

Links

Michael S. Branicky, Table of n, a(n) for n = 1..26

Prog

(PARI) n10np1(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 9, y=10^(x+1)*k+floor(10^x*d/9)*10+k; if(isprime(y), print1(y", ")) ) ) }
(Python)
from sympy import isprime
from itertools import count, islice
def agen(): yield from (t for i in count(1) for f in "1379" if isprime(t:=int(f + "8"*i + f)))
print(list(islice(agen(), 10))) # Michael S. Branicky, Jan 27 2023

Crossrefs

Similar sequences for digit d: A108845 (d=1), A108846 (d=2), A108841 (d=4), A108842 (d=5), A108843 (d=6), A108844 (d=7), A108848 (d=9).

Sequence in context: A142030 A267542 A082444 * A063360 A217499 A113156

Adjacent sequences: A108844 A108845 A108846 * A108848 A108849 A108850

Keyword

easy,nonn,base

Author

Cino Hilliard, Jul 11 2005

Extensions

Name changed by Arkadiusz Wesolowski, Sep 07 2011

One comment moved to A068689 by Michel Marcus, Jan 28 2023

Status

approved