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 A217197 #14 Sep 29 2012 18:18:41 %S A217197 13,29,61,109,137,149,181,197,229,257,277,281,317,349,389,401,457,461, %T A217197 541,557,569,617,677,761,797,821,929,937,977,1021,1097,1129,1217,1237, %U A217197 1289,1297,1321,1481,1489,1549,1597,1621,1721,1777,1861,1877,1997,2029 %N A217197 Primes p such that p-3 is the greatest semiprime less than p. %C A217197 Subsequence of A089531. %H A217197 T. D. Noe, <a href="/A217197/b217197.txt">Table of n, a(n) for n = 1..1000</a> %e A217197 977 is prime, 976 = 2^4*61 and 975 = 3*5^2*13 are not semiprimes, 974 = 2*487 is a semiprime. %t A217197 SemiPrimeQ[n_Integer] := If[Abs[n] < 2, False, (2 == Plus @@ Transpose[FactorInteger[Abs[n]]][[2]])]; Select[Prime[Range[500]], ! SemiPrimeQ[# - 1] && ! SemiPrimeQ[# - 2] && SemiPrimeQ[# - 3] &] (* _T. D. Noe_, Sep 27 2012 *) %o A217197 (PARI) forprime(p=5, 9999, bigomega(p-3)==2 && bigomega(p-1)!=2 && bigomega(p-2)!=2 & print1(p", ")) %Y A217197 Cf. A217195. %K A217197 nonn %O A217197 1,1 %A A217197 _Antonio Roldán_, Sep 27 2012