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 A377365 #6 Nov 04 2024 22:29:25
%S A377365 1,2,1,1,2,1,1,2,3,1,4,2,1,2,1,3,8,1,1,1036,1,3,2,1,1,2,1,1,2,4,1,2,1,
%T A377365 3,6,2,257,2,2,1,40,1,1,4,2,1,2,10,1,4,2,1,6,1,3,2,1,15,4,1,79,48,1,1,
%U A377365 2,1,5,6,1,1,6,4,3,2,1,1,2,3,3,2,1,1,6
%N A377365 a(n) = least k such that 2n*5^k+1 is prime, or 0 if no prime is reached.
%e A377365 a(20) = 1036 because 40*5^k+1 is prime for k=1036 and not prime for k=1..1035.
%t A377365 f[n_, k_] := 2 n*5^k + 1;
%t A377365 s[n_] := Select[Range[5000], PrimeQ[f[n, #]] &, 1];
%t A377365 Flatten[Table[s[n], {n, 1, 500}]]
%Y A377365 Cf. A000040, A050412, A354747, A377364, A377366, A377367.
%K A377365 nonn
%O A377365 1,2
%A A377365 _Clark Kimberling_, Oct 31 2024