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 A174840 #7 Mar 13 2023 11:47:23
%S A174840 3,7,9,13,26,26,42,32,65,63,84,74,89,162,110,126,177,169,144,171,214,
%T A174840 196,237,238,323,297,363,344,327,515,441,543,420,481,612,494,604,543,
%U A174840 646,552,645,644,519,742,593,737,644,851,1012,787,1204,727,899,800,1046
%N A174840 Least k such that the primes 3 to prime(k+1) form a complete residue system (mod prime(n)).
%C A174840 If the value of the terminal prime is given rather than its index in the list of odd primes, the sequence becomes 7 19 29 43 103 103 191 137 347 311 439
%C A174840 In other words, the odd primes no larger than 7 form a complete residue set mod 3, the odd primes no larger than 19 form a complete residue set mod 5, and so forth
%t A174840 Table[p=Prime[n]; k=1; While[u=Union[Mod[Prime[Range[2,k]], p]]; u != Range[0,p-1], k++ ]; k-1, {n,2,100}] (* _T. D. Noe_, Apr 02 2010 *)
%K A174840 nonn
%O A174840 1,1
%A A174840 _Keith Backman_, Mar 30 2010
%E A174840 Name improved by _T. D. Noe_, Apr 05 2010
%E A174840 Corrected and extended by _T. D. Noe_, Apr 02 2010