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 A131489 #19 Jun 17 2025 11:55:56
%S A131489 3,18,1728,679477248
%N A131489 Partial products of A092680.
%C A131489 _Max Alekseyev_ points out that every term of A066466, except 4, must be of the form 3*2^k such that 3*2^(k+1)-1, 3*2^(k+1)+1 are twin primes. There are no such new k+1 (i.e., except known 1,2,6,18) below 1000. In other words, 3*2^n - 1, 3*2^n + 1 are twin primes for n=1,2,6,18. According to these tables in the Keller links there are no other such n up to 18*10^6. Therefore the next term of A066466 (if it exists) is greater than 3*2^(18*10^6) ~= 10^5418540. Hence the next element of the anti-primorials (if it exists) is greater than 679477248 * 10^5418540 > 10^5418548. [Updated by _Max Alekseyev_, May 23 2023]
%H A131489 Ray Ballinger and Wilfrid Keller, <a href="http://www.prothsearch.com/riesel1.html">List of primes k.2^n + 1 for k < 300</a>
%H A131489 Wilfrid Keller, <a href="http://www.prothsearch.com/riesel2.html">List of primes k.2^n - 1 for k < 300</a>
%F A131489 a(n) = Product_{k=1..n} A092680(k).
%e A131489 a(1) = 3.
%e A131489 a(2) = 3 * 6 = 18.
%e A131489 a(3) = 3 * 6 * 96 = 1728.
%e A131489 a(4) = 3 * 6 * 96 * 393216 = 679477248.
%Y A131489 Cf. A092680.
%K A131489 nonn
%O A131489 1,1
%A A131489 _Jonathan Vos Post_, Jul 28 2007