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%I #8 Jun 30 2022 10:25:18
%S 4,6,9,99,111,4444,111111111,555555555555,9999999999999999,
%T 111111111111111111,444444444444444444,555555555555555555555,
%U 777777777777777777777777,333333333333333333333333333333333,444444444444444444444444444444444444
%N Repdigits which are the average of two successive primes.
%H Michael S. Branicky, <a href="/A104389/b104389.txt">Table of n, a(n) for n = 1..31</a>
%F a(n) = (A104387(n)+A104388(n))/2.
%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 r
%o print(list(islice(agen(), 15))) # _Michael S. Branicky_, Jun 30 2022
%Y Corresponding primes: A104387, A104388.
%Y Cf. A054268, A104386, A104387, A104388.
%K nonn,base
%O 1,1
%A _Zak Seidov_, Mar 04 2005
%E More terms from _Giovanni Resta_, Apr 05 2006