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 A109504 #12 Apr 12 2021 15:00:54 %S A109504 13,19,53,89,251,701,1709,1889,2699,5669,12401,13859,18719,38501, %T A109504 49139,60029,104651,114479,146609,158201,188189,226799,258119,371951, %U A109504 385001,497501,597869,665279,954269,1034639,1159001,1309769,1660751,1869209 %N A109504 Chen primes p such that p + 2 is triangular. %H A109504 Amiram Eldar, <a href="/A109504/b109504.txt">Table of n, a(n) for n = 1..10000</a> %e A109504 a(9) = 2699 because it is prime and 2701 = 37*73 and 73*74/2 = 2701. %t A109504 tri[n_] := n*(n + 1)/2; Select[tri /@ Range[2000] - 2, PrimeQ[#] && PrimeOmega[# + 2] == 2 &] (* _Amiram Eldar_, Dec 17 2019 *) %t A109504 Select[Prime[Range[150000]],(PrimeQ[#+2]|| PrimeOmega[#+2]==2)&&OddQ[Sqrt[ 1+8(#+2)]]&] (* _Harvey P. Dale_, Apr 12 2021 *) %Y A109504 Cf. A000217, A109611. %K A109504 easy,nonn %O A109504 1,1 %A A109504 _Jason Earls_, Aug 29 2005