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 A144482 #16 Dec 30 2020 15:29:03 %S A144482 9,21,49,93,217,381,889,961,3937,16129,24573,57337,253921,393213, %T A144482 917497,1040257,1572861,3670009,4063201,16252897,16646017,66584449, %U A144482 67092481,1073602561,4294434817,6442450941,15032385529,17179607041 %N A144482 Semiprimes that are a product of Mersenne primes. %C A144482 As the product of any two primes is semiprime by definition, this is also the list of composite numbers n=x*y where both x and y are Mersenne primes. - _Christian N. K. Anderson_, Mar 25 2013 %H A144482 Christian N. K. Anderson, <a href="/A144482/b144482.txt">Table of n, a(n) for n = 1..75</a> %t A144482 Take[Times@@@Tuples[2^# -1&/@MersennePrimeExponent[Range[10]],2]//Union,30] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Dec 30 2020 *) %o A144482 (PARI) %o A144482 isA000668(n) = (isprime(n)&&!bitand(n,1+n)); %o A144482 isA144482(n) = ((2==bigomega(n))&&isA000668(vecmin(factor(n)[,1]))&&isA000668(vecmax(factor(n)[,1]))); \\ _Antti Karttunen_, Jun 28 2020 %Y A144482 Cf. A000668, A001358, A144856, A333788. %Y A144482 Subsequence of A335882. %K A144482 nonn %O A144482 1,1 %A A144482 _G. L. Honaker, Jr._, Oct 12 2008