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 A158962 #7 Apr 14 2021 19:16:31 %S A158962 3,4,4,444,827868,10387692,1885781034 %N A158962 a(n) is the smallest number m such that all n numbers m-1, m.m-1, ..., m.m. .. .m-1 are prime, where dot means concatenation. %e A158962 All 4 numbers 444-1,444444-1,1+444444444-1,444444444444-1 are prime and 444 %e A158962 is the smallest such number so a(4)=444. %p A158962 a:= proc(n) local m; for m do if andmap(isprime, %p A158962 [seq(parse(cat(m$i))-1, i=1..n)]) then return m fi od %p A158962 end: %p A158962 seq(a(n), n=1..5); # _Alois P. Heinz_, Apr 14 2021 %o A158962 (Python) %o A158962 from sympy import isprime %o A158962 def A158962(n): %o A158962 m = 1 %o A158962 while True: %o A158962 for i in range(n): %o A158962 if not isprime(int(str(m)*(i+1))-1): %o A158962 break %o A158962 else: %o A158962 return m %o A158962 m += 1 # _Chai Wah Wu_, Apr 14 2021 %Y A158962 Cf. A153434. %K A158962 base,more,nonn %O A158962 1,1 %A A158962 _Farideh Firoozbakht_, Apr 02 2009