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 A172187 #11 Mar 22 2020 09:26:03
%S A172187 13,22,37,58,73,85,94,122,130,137,157,166,181,193,202,229,237,238,253,
%T A172187 262,265,301,302,310,318,346,373,382,409,418,433,437,445,454,462,465,
%U A172187 481,514,517,526,537,541,553,562,589,598,634,661,662,670,697,706,733
%N A172187 Numbers k such that k and k+1 are squarefree but 2*k+1 is not.
%H A172187 Amiram Eldar, <a href="/A172187/b172187.txt">Table of n, a(n) for n = 1..10000</a>
%t A172187 Select[Range[750], And @@ SquareFreeQ /@ {#, # + 1} && !SquareFreeQ[2# + 1] &] (* _Amiram Eldar_, Mar 22 2020 *)
%Y A172187 Complement of A007674 and A172186.
%K A172187 nonn
%O A172187 1,1
%A A172187 _Artur Jasinski_, Jan 28 2010