A104388 - OEIS

%I #15 Jun 30 2022 10:41:50

%S 3,5,7,97,109,4441,111111109,555555555551,9999999999999937,

%T 111111111111111091,444444444444444419,555555555555555555491,

%U 777777777777777777777767,333333333333333333333333333333293,444444444444444444444444444444444391

%N Lesser of two successive primes the average of which is a repdigit.

%H Chai Wah Wu, <a href="/A104388/b104388.txt">Table of n, a(n) for n = 1..31</a>

%F a(n) = prime(A104386(n)).

%o (Python)

%o from itertools import count, islice

%o from sympy import isprime, prevprime

%o def agen():

%o     for d in count(1):

%o         ru = int("1"*d)

%o         for r in range(ru, 10*ru, ru):

%o             if r > 2:

%o                 p = prevprime(r)

%o                 if isprime(r + (r-p)) and prevprime(r+(r-p)) == p:

%o                     yield p

%o print(list(islice(agen(), 15))) # _Michael S. Branicky_, Jun 30 2022

%Y Cf. A054268, A104386, A104387 (larger primes), A104389 (repdigits).

%K nonn,base

%O 1,1

%A _Zak Seidov_, Mar 04 2005

%E More terms from _Giovanni Resta_, Feb 09 2006