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 A340509 #18 Jul 09 2025 04:55:02
%S A340509 5,8,20,56,92,110,236,290,416,470,596,632,686,812,920,992,1010,1100,
%T A340509 1136,1316,1496,1640,1730,1802,1820,1856,1982,2072,2180,2432,2486,
%U A340509 2630,2810,2900,2990,3026,3206,3512,3710,3836,3890,4196,4286,4376,4592,4826,4880,4970,5276,5600
%N A340509 a(n) = 3*A005382(n)-1.
%C A340509 These are the numbers b(n) + 2*b(n)-1, where b is A005382, and so form a potentially infinite sequence of numbers which are the sum of two primes. An analog of A175666.
%F A340509 a(n) = A005383(n) + A005382(n). - _Wesley Ivan Hurt_, Feb 22 2022
%p A340509 q:= p-> isprime(2*p-1):
%p A340509 map(x-> 3*x-1, select(q, [ithprime(i)$i=1..300]))[]; # _Alois P. Heinz_, Jan 27 2021
%t A340509 Select[Range[5600], And @@ PrimeQ[{# + 1, 2*# - 1}/3] &] (* _Amiram Eldar_, Jan 27 2021 *)
%Y A340509 Cf. A005382, A005383, A005384, A175666.
%K A340509 nonn
%O A340509 1,1
%A A340509 _N. J. A. Sloane_, Jan 27 2021, following a suggestion from _Des MacHale_