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 A032623 #15 Nov 25 2023 17:07:26
%S A032623 1,3,13,15,21,39,49,55,69,75,91,111,115,159,163,165,169,171,183,193,
%T A032623 195,199,201,205,211,229,235,241,249,265,271,273,289,291,309,313,319,
%U A032623 321,325,331,333,349,351,355,363,379,381,385,391,393,405,423,441,445
%N A032623 Numbers k such that k concatenated with k+8 is a prime.
%H A032623 Harvey P. Dale, <a href="/A032623/b032623.txt">Table of n, a(n) for n = 1..1000</a>
%t A032623 Select[Range[500],PrimeQ[FromDigits[Flatten[IntegerDigits/@{#,#+8}]]]&] (* _Harvey P. Dale_, Nov 25 2023 *)
%Y A032623 Cf. A032613.
%K A032623 nonn,base
%O A032623 1,2
%A A032623 _Patrick De Geest_, May 15 1998