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 A124940 #13 Dec 07 2024 14:56:09 %S A124940 27,42,63,75,99,102,114,171,172,242,255,258,279,282,322,354,363,366, %T A124940 385,399,423,425,426,435,452,474,531,575,595,602,603,606,615,639,642, %U A124940 651,654,665,722,759,772,830,844,894,903,906,932,935,978 %N A124940 Numbers k such that k and k+3 are 3-almost primes. %H A124940 Charles R Greathouse IV, <a href="/A124940/b124940.txt">Table of n, a(n) for n = 1..10000</a> %e A124940 27=3*3*3, 30=2*3*5; 42=2*3*7, 45=3*3*5. %t A124940 Select[Range[1000], PrimeOmega[#]==PrimeOmega[#+3]==3 &] (* _James C. McMahon_, Dec 07 2024 *) %o A124940 (PARI) isok(n) = (bigomega(n) == 3) && (bigomega(n+3) == 3); \\ _Michel Marcus_, Oct 11 2013 %Y A124940 Cf. A124941, A124942. %K A124940 nonn %O A124940 1,1 %A A124940 _Zak Seidov_, Nov 13 2006