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 A173087 #15 Sep 08 2022 08:45:50
%S A173087 82,142,214,254,326,358,386,478,538,542,566,674,758,802,974,1198,1366,
%T A173087 1466,1594,1754,1762,1942,2302,2342,2374,2582,2654,2746,2762,2818,
%U A173087 2998,3106,3134,3418,3494,3518,3554,3566,3646,3734,3778,3862,4138,4178,4258
%N A173087 Semiprimes k such that k^2 - 7 and k^2 + 7 are also semiprime.
%H A173087 Harvey P. Dale, <a href="/A173087/b173087.txt">Table of n, a(n) for n = 1..500</a>
%e A173087 82 = 2*41, 82^2 - 7 = 6717 = 3*2239 and 82^2 + 7 = 6731 = 53*127 are all semiprime, hence 82 is a term.
%t A173087 f[n_]:=Last/@FactorInteger[n]=={1,1}||Last/@FactorInteger[n]=={2}; lst={};Do[If[f[n], a=n^2-7;b=n^2+7;If[f[a]&&f[b],AppendTo[lst,n]]],{n,8!}];lst
%t A173087 Select[Range[4500],Thread[PrimeOmega[{#,#^2-7,#^2+7}]]=={2,2,2}&] (* _Harvey P. Dale_, Jul 27 2022 *)
%o A173087 (Magma) IsSemiprime:=func< n | &+[ k[2]: k in Factorization(n) ] eq 2 >; [ n: n in [2..4300] | IsSemiprime(n) and IsSemiprime(n^2-7) and IsSemiprime(n^2+7) ]; // _Klaus Brockhaus_, Feb 25 2010
%Y A173087 Cf. A001358, A173082, A173083, A173084, A173085, A173086.
%K A173087 nonn
%O A173087 1,1
%A A173087 _Vladimir Joseph Stephan Orlovsky_, Feb 09 2010
%E A173087 Edited by _Klaus Brockhaus_ and _N. J. A. Sloane_, Feb 25 2010