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 A306220 #21 Jun 18 2020 16:33:53 %S A306220 3,5,2,3,2,13,3,5,7,3,2,5,2,11,7,3,5,5,2,11,2,3,5,13,3,11,2,3,2,7,3,5, %T A306220 5,3,2,7,2,5,7,3,13,5,2,7,2,3,5,5,3,7,2,3,2,13,3,11,5,3,2,7,2,5,5,3,7, %U A306220 19,2,5,2,3,7,5,3,7,2,3,2,5,3,11,7,3,2,13,2,7,5 %N A306220 a(n) is the smallest prime p such that Kronecker(-n,p) = -1. %C A306220 A companion sequence to A092419. %C A306220 Conjecture: lim sup log(a(n))/log(n) = 0. For example, it seems that log(a(n))/log(n) < 0.5 for all n > 1364. %H A306220 Robert Israel, <a href="/A306220/b306220.txt">Table of n, a(n) for n = 1..10000</a> %F A306220 a(n) = 2 if and only if n == 3, 5 (mod 8). See A047621. %F A306220 a(n) = 3 if and only if n == 1, 4, 7, 10, 16, 22 (mod 24). %p A306220 # This requires Maple 2016 or later %p A306220 f:= proc(n) local p; %p A306220 p:= 2; %p A306220 while NumberTheory:-KroneckerSymbol(-n,p) <> -1 do p:= nextprime(p) od: %p A306220 p %p A306220 end proc: %p A306220 map(f, [$1..100]); # _Robert Israel_, Feb 17 2019 %t A306220 a[n_] := For[p = 2, True, p = NextPrime[p], If[KroneckerSymbol[-n, p] == -1, Return[p]]]; %t A306220 Array[a, 100] (* _Jean-François Alcover_, Jun 18 2020 *) %o A306220 (PARI) a(n) = forprime(p=2, , if(kronecker(-n, p)<0, return(p))) %Y A306220 Cf. A092419. %Y A306220 See A306224 for another version. %K A306220 nonn %O A306220 1,1 %A A306220 _Jianing Song_, Jan 29 2019