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 A117328 #9 Oct 15 2017 13:29:28 %S A117328 29,53,61,73,89,137,173,181,263,331,449,523,541,547,569,577,587,593, %T A117328 683,691,727,811,839,947,1051,1063,1153,1163,1223,1259,1289,1367,1531, %U A117328 1559,1627,1637,1847,1861,1933,1973,1987,2099,2153,2161,2213,2267,2287,2311 %N A117328 Primes p such that p +- 4 are semiprimes. %C A117328 Cf. A063643 Primes p such that p +- 2 are semiprimes. %H A117328 Harvey P. Dale, <a href="/A117328/b117328.txt">Table of n, a(n) for n = 1..1000</a> %e A117328 29 - 4 = 25 = 5*5 (semiprime). 29 + 4 = 33 = 3*11 (semiprime). %t A117328 fQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; Select[ Prime@ Range[3, 345], fQ[ # - 4] && fQ[ # + 4] &] (* _Robert G. Wilson v_, May 01 2006 *) %t A117328 Select[Prime[Range[400]],PrimeOmega[#-4]==PrimeOmega[#+4]==2&] (* _Harvey P. Dale_, Oct 15 2017 *) %Y A117328 Cf. A063643. %K A117328 nonn %O A117328 1,1 %A A117328 _Zak Seidov_, Mar 08 2006