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 A086816 #14 Sep 18 2024 14:15:31
%S A086816 17,59,137,149,1277,1619,2729,4127,6359,11717,13397,17489,20807,23027,
%T A086816 28307,29669,51869,61379,69827,73847,78539,92567,97499,115769,138569,
%U A086816 166667,176609,193379,200927,258317,304979,430007,500909,518759,536189
%N A086816 Smaller member of a twin prime pair with a triangular sum.
%C A086816 It is easily shown that all terms end in 7 or 9.
%H A086816 Harvey P. Dale, <a href="/A086816/b086816.txt">Table of n, a(n) for n = 1..300</a>
%F A086816 a(n) = 6*A166119(n) - 1. - _Hugo Pfoertner_, Sep 18 2024
%e A086816 59 is a term because it is the smaller member of the twin prime pair (59,61) and 59 + 61 = 120 = 15*(15+1)/2.
%t A086816 Transpose[Select[Partition[Prime[Range[45000]],2,1],#[[2]]-#[[1]]==2 && IntegerQ[(Sqrt[1+8Total[#]]-1)/2]&]][[1]] (* _Harvey P. Dale_, Dec 15 2011 *)
%o A086816 (PARI) lista(n)={my(L=List(), k=0); while(#L<n, k++; my(t=k*(k+1)/4); if(!frac(t)&&isprime(t-1)&&isprime(t+1), listput(L,t-1))); Vec(L)} \\ _Andrew Howroyd_, Sep 18 2024
%Y A086816 Cf. A000217, A001359, A166119.
%K A086816 nonn
%O A086816 1,1
%A A086816 _Jason Earls_, Aug 06 2003
%E A086816 Offset changed by _Andrew Howroyd_, Sep 18 2024