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 A291318 #14 Aug 23 2017 03:15:45
%S A291318 4,9,15,33,35,49,51,65,77,87,91,95,119,123,143,161,177,185,209,213,
%T A291318 215,217,221,247,259,287,303,321,329,335,341,361,371,377,395,403,407,
%U A291318 411,427,437,447,469,473,485,511,515,527,533,537,545,551,573,581,591,611,629
%N A291318 Semiprimes of the form p*q such that p+q-1 is prime.
%C A291318 Obviously, 4 is the only even term.
%C A291318 The terms divisible by 3 are 3*A001359. - _Robert Israel_, Aug 22 2017
%H A291318 Charles R Greathouse IV, <a href="/A291318/b291318.txt">Table of n, a(n) for n = 1..10000</a>
%e A291318 4 = 2*2 and 2+2-1 is prime, so 4 is a term.
%e A291318 185 = 5*37 and 5+37-1 is prime, so 185 is a term.
%p A291318 N:= 1000: # to get terms <= N
%p A291318 OddPrimes:= select(isprime, [seq(i,i=3..N/3,2)]):
%p A291318 R:= select(t -> t[1]*t[2]<= N and isprime(t[1]+t[2]-1), [[2,2],seq(seq([OddPrimes[i],OddPrimes[j]],j=1..i),i=1..nops(OddPrimes))]):
%p A291318 sort(map(t -> t[1]*t[2],R)); # _Robert Israel_, Aug 22 2017
%t A291318 With[{nn=60}, Take[#, nn]&@Union@Flatten@Table[Function[p, Map[Times@@#&@#&, #]&@Select[Map[{p, #}&, Prime@Range[PrimePi@p]], PrimeQ[Total@# - 1] &]]@Prime@n,{n, nn + 4}]]
%t A291318 (* Second program: *)
%t A291318 Select[Range@ 630, And[Length@ # == 2, PrimeQ[First@ # + Last@ # - 1]] &@
%t A291318 Flatten@Map[ConstantArray[#1, #2] & @@ # &, FactorInteger[#]] &] (* _Michael De Vlieger_, Aug 22 2017 *)
%o A291318 (PARI) list(lim)=my(v=List([4])); forprime(p=3,lim\3, forprime(q=3,min(lim\p,p), if(isprime(p+q-1), listput(v,p*q)))); Set(v) \\ _Charles R Greathouse IV_, Aug 23 2017
%Y A291318 Cf. A001358, A001359, A290434.
%K A291318 nonn,easy
%O A291318 1,1
%A A291318 _Vincenzo Librandi_, Aug 22 2017