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 A306502 #14 Mar 24 2020 06:39:59
%S A306502 1,102091236,732722,6181,314,1,199,3,2,128,1,5,2,1,4,7,5,1,4,3,1,6,1,
%T A306502 2,9,4,2,1,6,8,1,9,7,1,3,1,4,2,1,6,2,1,8,4,1,11,11,3,7,1,6,6,2,15,1,3,
%U A306502 2,1,12,1,15,1,3,4,1,14,1,2,5,3,2,1,10,16,1,13,1,8,1
%N A306502 a(n) is the index in primes of A306499(n), or 0 if A306499(n) = 0.
%C A306502 a(n) is the smallest integer k such that Sum_{i=1..k} Kronecker(A003658(n),prime(i)) > 0, or 0 if no such k exists.
%C A306502 See A306499 for the actual primes.
%e A306502 See A306499 for the example that shows a(16) = 7.
%o A306502 (PARI) b(n) = my(i=0); forprime(p=2, oo, i+=kronecker(n, p); if(i>0, return(p)))
%o A306502 for(n=1, 300, if(isfundamental(n), print1(primepi(b(n)), ", ")))
%o A306502 (Sage) # uses[KroneckerSum from A306499]
%o A306502 A306499 = KroneckerSum()
%o A306502 print([prime_pi(next(A306499)) for _ in range(77)]) # _Peter Luschny_, Feb 26 2019
%Y A306502 Cf. A003658, A306499, A306503.
%K A306502 nonn
%O A306502 1,2
%A A306502 _Jianing Song_, Feb 19 2019