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 A115765 #6 Feb 03 2023 04:55:39
%S A115765 3,7,5,17,29,5,509,1013,1109
%N A115765 Triangle read by rows: row n (n>=2) gives a set of n primes with the property that the averages of all subsets are all primes, having the smallest largest element.
%C A115765 See A113833 for the case of all subset averages being distinct primes. The Mathematica program is for row 4.
%H A115765 Andrew Granville, <a href="http://www.dms.umontreal.ca/~andrew/PDF/PrimePatterns.pdf">Prime number patterns</a>
%e A115765 The set of primes generated by {5, 17, 29} is {5, 11, 17, 17, 17, 23, 29}.
%e A115765 Triangle begins:
%e A115765 3, 7
%e A115765 5, 17, 29
%e A115765 5, 509, 1013, 1109
%t A115765 Needs["DiscreteMath`Combinatorica`"]; nn=PrimePi[1277]; Do[s=Prime[{l, k, j, i}]; ss=Rest[Subsets[s]]; ave=(Plus@@@ss)/(Length/@ss); If[And@@(IntegerQ/@ave) && And@@PrimeQ[ave], Break[]], {l, 2, nn}, {k, 2, l-1}, {j, 2, k-1}, {i, 2, j-1}]; Reverse[s]
%K A115765 nonn,tabf,hard,more
%O A115765 2,1
%A A115765 _T. D. Noe_, Jan 30 2006