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 A370008 #9 Feb 16 2024 15:07:51
%S A370008 5,7,13,19,31,37,47,53,67,83,89,109,113,127,139,157,173,181,199,211,
%T A370008 211,233,241,263,283,293,307,317,317,337,379,389,409,409,443,449,467,
%U A370008 487,499,509,523,541,571,577,587,593,631,661,677,683,691,709,719,751
%N A370008 a(n) is the greatest prime less than 3*prime(n).
%e A370008 5 < 3*2 < 7 < 3*3 < 11 < 13 < 3*5, so (a(1), a(2), a(3)) = (5,7,13).
%t A370008 Table[Prime[PrimePi[3*Prime[n]]], {n,1,200}]
%o A370008 (PARI) a(n) = precprime(3*prime(n)); \\ _Michel Marcus_, Feb 10 2024
%Y A370008 Cf. A000040, A001748, A059786, A059788, A370009.
%K A370008 nonn
%O A370008 1,1
%A A370008 _Clark Kimberling_, Feb 09 2024