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 A180641 #9 Oct 07 2013 03:22:20
%S A180641 7,17,19,31,41,53,71,79,89,97,101,109,127,151,163,181,191,197,199,239,
%T A180641 241,251,257,271,307,337,349,379,401,419,431,433,449,461,463,487,491,
%U A180641 499,521,571,577,593,599,601,631,641,647,659,683,701,727,751,769,809
%N A180641 Primes P such that P > (largest prime factor of (P-1)) * (largest prime factor of (P+1)).
%H A180641 Harvey P. Dale, <a href="/A180641/b180641.txt">Table of n, a(n) for n = 1..1000</a>
%e A180641 Example: For n = 3, a(3)=19.
%e A180641 The prime P = 19
%e A180641 P-1 = 18 (largest prime factor of 18 is 3)
%e A180641 P+1 = 20 (largest prime factor of 20 is 5)
%e A180641 19 > 3*5.
%t A180641 lpfQ[n_]:=Module[{a=FactorInteger[n-1][[-1,1]],b=FactorInteger[n+1][[-1,1]]},n>a*b]; Select[Prime[Range[200]],lpfQ] (* _Harvey P. Dale_, Aug 16 2013 *)
%o A180641 (PARI) lpf(n) = {f = factor(n); return (f[#f~, 1]);}
%o A180641 lista(nn) = {forprime(p=3, nn,if ((p > lpf(p-1)*lpf(p+1)), print1(p, ", ");););} \\ _Michel Marcus_, Jul 25 2013
%Y A180641 Cf. A180640. See also A103666, A103667.
%K A180641 nonn
%O A180641 1,1
%A A180641 _Karl Hovekamp_, Sep 14 2010