This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A104386 #25 Jun 02 2024 08:23:15
%S A104386 2,3,4,25,29,603,6363181,21366409911,279238341033925,2907021742443974,
%T A104386 11220808305309952,11885037375341198280
%N A104386 Numbers k such that the average of the k-th and (k+1)-th primes is a repdigit.
%F A104386 (prime(k) + prime(k+1))/2 = repdigit.
%o A104386 (Python)
%o A104386 from itertools import count, islice
%o A104386 from sympy import isprime, prevprime, primepi
%o A104386 def agen():
%o A104386 for d in count(1):
%o A104386 ru = int("1"*d)
%o A104386 for r in range(ru, 10*ru, ru):
%o A104386 if r > 2:
%o A104386 p = prevprime(r)
%o A104386 if isprime(r + (r-p)) and prevprime(r+(r-p)) == p:
%o A104386 yield primepi(p)
%o A104386 print(list(islice(agen(), 7))) # _Michael S. Branicky_, Jun 30 2022
%Y A104386 Cf. A054268.
%Y A104386 Corresponding primes A104387, A104388, repdigits A104389.
%K A104386 nonn,base,hard,more
%O A104386 1,1
%A A104386 _Zak Seidov_, Mar 04 2005
%E A104386 a(8) from _Giovanni Resta_, Apr 05 2006
%E A104386 a(9) from _Michael S. Branicky_, Jul 02 2022
%E A104386 a(10)-a(12) from _Chai Wah Wu_, Jun 01 2024