%I #20 Jul 02 2022 09:29:14
%S 2,3,4,25,29,603,6363181,21366409911,279238341033925
%N Numbers k such that the average of the kth and (k+1)th primes is a repdigit.
%F (prime(k) + prime(k+1))/2 = repdigit.
%o (Python)
%o from itertools import count, islice
%o from sympy import isprime, prevprime, primepi
%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 + (rp)) and prevprime(r+(rp)) == p:
%o yield primepi(p)
%o print(list(islice(agen(), 7))) # _Michael S. Branicky_, Jun 30 2022
%Y Cf. A054268.
%Y Corresponding primes A104387, A104388, repdigits A104389.
%K nonn,base,hard,more
%O 1,1
%A _Zak Seidov_, Mar 04 2005
%E a(8) from _Giovanni Resta_, Apr 05 2006
%E a(9) from _Michael S. Branicky_, Jul 02 2022
