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 A062721 #18 May 08 2021 22:55:35
%S A062721 4,9,15,21,25,33,39,49,55,69,85,91,111,115,129,133,141,159,169,183,
%T A062721 201,213,235,253,259,265,295,309,319,339,355,361,381,391,403,411,445,
%U A062721 451,469,481,489,493,501,505,511,543,559,565,573,579,589,633,649,655,679
%N A062721 Numbers k such that k is a product of two primes and k-2 is prime.
%C A062721 This sequence is a subsequence of A107986, which only requires k to be composite. The first term in that sequence which is not in this sequence is 45, a number with three prime factors. - _Alonso del Arte_, May 03 2014
%H A062721 Zak Seidov, <a href="/A062721/b062721.txt">Table of n, a(n) for n = 1..10000</a>.
%t A062721 Select[ Range[ 2, 1500 ], Plus @@ Last@Transpose@FactorInteger[ # ] == 2 && PrimeQ[ # - 2 ] & ]
%t A062721 Select[Range[700], PrimeOmega[#] == 2 && PrimeQ[# - 2]&] (* _Harvey P. Dale_, Mar 25 2013 *)
%o A062721 (PARI) { n=0; for (m=1, 10^9, a=prime(m) + 2; f=factor(a)~; if ((length(f)==1 && f[2, 1]==2) || (length(f)==2 && f[2, 1]==1 && f[2, 2]==1), write("b062721.txt", n++, " ", a); if (n==10000, break)) ) } \\ _Harry J. Smith_, Aug 09 2009
%Y A062721 Cf. A006512, A001358, A043326.
%Y A062721 Cf. A063637, A046315, A089268.
%K A062721 nonn,easy
%O A062721 1,1
%A A062721 Ahmed Fares (ahmedfares(AT)my-deja.com), Jul 14 2001