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 A164698 #10 Feb 15 2020 10:52:27 %S A164698 6,21,26,51,1157,372101,1288005205276048901 %N A164698 Semiprimes pq such that pq - 1 divides p^2 + q^2 + 2. %C A164698 Semiprimes pq such that pq-1 divides (p+q)^2. %C A164698 The third to fifth terms are Fib(3)*Fib(7), Fib(7)*Fib(11) and Fib(13)*Fib(17). %C A164698 Products of two prime Fibonacci numbers F(k) and F(k+4) (see A001605 and A005478) are in the sequence. %C A164698 6 and 26 are the only even terms. Odd terms contain products of pairs of consecutive terms from the following sequences: A005248, A001541, A033889, A033891. - _Max Alekseyev_, Aug 27 2009 %e A164698 The semiprime 6 = 2*3 is in the sequence because 2*3 - 1 = 5 divides 2^2 + 3^2 + 2 = 15. %p A164698 isA001358 := proc(n) RETURN ( numtheory[bigomega](n) =2 ) ; end: %p A164698 isA164698 := proc(n) if isA001358(n) then p := op(1,op(1,ifactors(n)[2]) ) ; q := n/p ; if (p^2+q^2+2) mod (p*q-1) = 0 then true; else false; fi; else false; fi; end: %p A164698 for n from 4 to 3000000 do if isA164698(n) then print(n, ifactors(n)) ; fi; od: # _R. J. Mathar_, Aug 24 2009 %Y A164698 Cf. A001358, A000045, A140362, A164643. %K A164698 nonn,more %O A164698 1,1 %A A164698 _Mohamed Bouhamida_, Aug 22 2009 %E A164698 Missing values added by _R. J. Mathar_, Aug 24 2009 %E A164698 a(7) from _Max Alekseyev_, Aug 27 2009