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%I #17 Jun 30 2022 10:27:00
%S 5,7,11,101,113,4447,111111113,555555555559,10000000000000061,
%T 111111111111111131,444444444444444469,555555555555555555619,
%U 777777777777777777777787,333333333333333333333333333333373,444444444444444444444444444444444497
%N Larger of two successive primes the average of which is a repdigit.
%C Lesser primes A104388, repdigits A104389. What is the next term?
%C The next term is 444444444444444444444444444444444497. The first term with more than 100 digits is a(22) which has 109 digits. - _Harvey P. Dale_, Jun 28 2011
%H Michael S. Branicky, <a href="/A104387/b104387.txt">Table of n, a(n) for n = 1..31</a>
%F a(n) = prime(A104386(n)+1).
%t Union[Flatten[Table[NextPrime/@Select[FromDigits/@Table[PadLeft[{i},n,i], {n,45}], Mean[{NextPrime[#],NextPrime[#,-1]}]==#&], {i,9}]]] (* _Harvey P. Dale_, Jun 28 2011 *)
%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 2*r - p
%o print(list(islice(agen(), 15))) # _Michael S. Branicky_, Jun 30 2022
%Y Cf. A054268, A104386, A104388, A104389.
%K nonn,base
%O 1,1
%A _Zak Seidov_, Mar 04 2005
%E More terms from _Giovanni Resta_, Apr 05 2006
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