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 A264046 #10 Dec 24 2023 16:25:19 %S A264046 15,123,365,371,505,545,573,591,649,707,807,843,943,1067,1159,1247, %T A264046 1357,1405,1529,1555,1633,1739,1745,1829,1843,1897,1909,1985,2149, %U A264046 2159,2209,2285,2329,2353,2363,2407,2413,2463,2501,2643,2773,2779 %N A264046 Numbers k such that k and k+6 are consecutive semiprimes. %C A264046 Note that a(1) = 15 = A131109(k=6). %H A264046 Charles R Greathouse IV, <a href="/A264046/b264046.txt">Table of n, a(n) for n = 1..10000</a> %e A264046 15 = A001358(6) and 21 = A001358(7). %t A264046 Select[Partition[Select[Range[3000],PrimeOmega[#]==2&],2,1],#[[2]]-#[[1]]==6&][[;;,1]] (* _Harvey P. Dale_, Dec 24 2023 *) %o A264046 (PARI) is(n)=if(bigomega(n)!=2 || bigomega(n+6)!=2, return(0)); for(i=1,5,if(bigomega(n+i)==2, return(0))); 1 \\ _Charles R Greathouse IV_, Nov 02 2015 %Y A264046 Cf. A001358, A065516, A123375, A131109, A136196, A264043, A264044, A264045. %K A264046 nonn %O A264046 1,1 %A A264046 _Zak Seidov_, Nov 02 2015