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 A087865 #31 Jun 06 2024 14:18:53
%S A087865 2,53,16097,120739,334349,18703411700669
%N A087865 Prime numbers of the form primepi(3^m), for some integer m.
%C A087865 These are the prime terms in A055729.
%t A087865 Select[ Table[ PrimePi[ 3^n], {n, 0, 49}], PrimeQ@# &] (* _Robert G. Wilson v_, Feb 25 2010 *)
%o A087865 (PARI) primeslessxn2(n, p) = /*primes < p^n if prime */ { sr=0; for(x=0, n, y=primepi(p^x); if(y<>0, sr+=1.0/y); if(isprime(y), print1(y", ")); ); print(); print(sr) }
%o A087865 (Python)
%o A087865 from itertools import islice
%o A087865 from sympy import isprime, primepi
%o A087865 def A087865_gen(): # generator of terms
%o A087865 k = 1
%o A087865 while True:
%o A087865 k *= 3
%o A087865 if isprime(p:=primepi(k)):
%o A087865 yield p
%o A087865 A087865_list = list(islice(A087865_gen(),5)) # _Chai Wah Wu_, Jun 06 2024
%Y A087865 Cf. A055729 (number of primes <= 3^n).
%K A087865 nonn,more,hard
%O A087865 1,1
%A A087865 _Cino Hilliard_, Oct 27 2003
%E A087865 a(6) added by _David Baugh_, Mar 17 2015