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 A123921 #19 Sep 28 2019 06:08:37 %S A123921 13,25589,47051,67589,136889,313589,960389,1005971,1932017,2301251, %T A123921 2362331,6100889,6310061,6901091,7745051,8236817,9332987,10956089, %U A123921 13104389,16850987,19009589,19201841,19386371,19998701,20566079 %N A123921 Primes of form p*q - 2 where p and q are consecutive primes. %H A123921 T. D. Noe, <a href="/A123921/b123921.txt">Table of n, a(n) for n = 1..1000</a> %e A123921 211*223-2 = 47051. %p A123921 with (numtheory): for n from 1 to 1000 do if (tau(ithprime(n)*ithprime(n+1)-2)=2) then print(ithprime(n), ithprime(n+1), ithprime(n)*ithprime(n+1)-2); fi; od; %t A123921 Select[Times@@@Partition[Prime[Range[1500]],2,1]-2,PrimeQ] (* _Harvey P. Dale_, Feb 23 2012 *) %o A123921 (Haskell) %o A123921 a123921 n = a123921_list !! (n-1) %o A123921 a123921_list = filter ((== 1) . a010051) $ %o A123921 map (flip (-) 2) $ zipWith (*) a000040_list (tail a000040_list) %o A123921 -- _Reinhard Zumkeller_, Nov 11 2011 %o A123921 (PARI) p=2; forprime(q=3,1e5, if(isprime(t=p*q-2), print1(t", ")); p=q) \\ _Charles R Greathouse IV_, Apr 29 2015 %Y A123921 Cf. A048797, A048880. %K A123921 nice,nonn %O A123921 1,1 %A A123921 Ville Saalo (vsaalo(AT)iki.fi), Nov 19 2006