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 A239619 #23 Sep 08 2022 08:46:07
%S A239619 2,1,3,3,3,3,5,3,5,3,3,3,5,5,5,7,5,5,5,7,5,7,3,5,5,5,5,7,3,5,5,7,5,5,
%T A239619 7,7,7,3,5,5,7,5,5,5,7,5,7,7,7,7,9,9,9,5,5,5,7,3,5,5,5,7,5,7,7,7,5,5,
%U A239619 7,7,5,7,7,7,5,7,7,7,9,5,7,7,9,5,7,7,9
%N A239619 Base 3 sum of digits of prime(n).
%H A239619 Vincenzo Librandi, <a href="/A239619/b239619.txt">Table of n, a(n) for n = 1..10000</a>
%F A239619 a(n) = A053735(A000040(n)).
%e A239619 The fifth prime is 11, 11 in base 3 is (1,0,2) so a(5)=1+0+2=3.
%t A239619 Table[Plus @@ IntegerDigits[Prime[n], 3], {n, 1, 100}] (* _Vincenzo Librandi_, Mar 25 2014 *)
%o A239619 (Sage) [sum(i.digits(base=3)) for i in primes_first_n(200)]
%o A239619 (Magma) [&+Intseq(NthPrime(n),3): n in [1..100]]; // _Vincenzo Librandi_, Mar 25 2014
%o A239619 (PARI) a(n) = vecsum(digits(prime(n), 3)); \\ _Michel Marcus_, Mar 07 2020
%Y A239619 Cf. A007605, A014499, A053735.
%K A239619 nonn,base,easy
%O A239619 1,1
%A A239619 _Tom Edgar_, Mar 22 2014