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 A078722 #17 Sep 08 2022 08:45:08
%S A078722 3,5,11,19,37,59,83,113,163,211,269,337,409,487,587,673,787,907,1031,
%T A078722 1163,1301,1471,1613,1789,1997,2179,2381,2617,2801,3049,3319,3557,
%U A078722 3821,4091,4373,4673,4993,5323,5651,5981,6317,6691,7039,7487,7853,8269,8693,9109
%N A078722 a(n) = prime(n*(n+1)/2+2).
%C A078722 The sum of the reciprocals of the terms appears to converge.
%H A078722 Harvey P. Dale, <a href="/A078722/b078722.txt">Table of n, a(n) for n = 0..1000</a>
%t A078722 Prime[Accumulate[Range[0,50]]+2] (* _Harvey P. Dale_, Aug 16 2014 *)
%o A078722 (PARI) triprimes(n) = { sr = 0; for(j=0,n, x = j*(j+1)/2+2; z = prime(x); sr+=1.0/z; print1(z, ", "); ); print(); /* print(sr); */}
%o A078722 (Magma) [NthPrime(n*(n+1) div 2+2): n in [0..50]]; // _Vincenzo Librandi_, Jun 08 2016
%Y A078722 Cf. A000040.
%Y A078722 Apart from initial term, primes in second diagonal of triangle in A078721.
%K A078722 nonn,easy
%O A078722 0,1
%A A078722 _Cino Hilliard_, Dec 20 2002