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 A306204 #14 Jan 06 2021 02:05:03
%S A306204 1,5,8,5,5,5,8,8,8,7,9,2,5,6,3,8,7,7,6,9,7,8,6,3,7,0,2,3,2,1,9,2,3,8,
%T A306204 4,7,6,0,6,9,4,0,5,8,6,7,9,4,7,0,2,8,1,1,3,2,9,8,1,2,6,7,8,9,2,8,8,5,
%U A306204 9,7,5,4,5,7,6,7,8,5,5,6,9,0,5,3,5,0,0,7,9,1,1,7,9,9,3,5,6,1,9,5
%N A306204 Decimal expansion of Product_{p>=3} (1+1/p) over the Mersenne primes.
%C A306204 This is equal to Product_{q>=1} (1-1/2^q)^(-1) over all q with 2^q - 1 a Mersenne prime.
%H A306204 Tomohiro Yamada, <a href="/A306204/b306204.txt">Table of n, a(n) for n = 1..99</a>
%H A306204 Tomohiro Yamada, <a href="http://mathematica-pannonica.ttk.pte.hu/index_elemei/mp19-1/MP19-1(2008)pp37-47.pdf">Unitary super perfect numbers</a>, Mathematica Pannonica, Volume 19, No. 1, 2008, pp. 37-47, using this constant with only a rough upper bound (4/3)*exp(4/21) < 1.6131008.
%F A306204 Equals Sum_{n>=1} 1/A046528(n). - _Amiram Eldar_, Jan 06 2021
%e A306204 Decimal expansion of (4/3) * (8/7) * (32/31) * (128/127) * (8192/8191) * (131072/131071) * (524288/524287) * ... = 1.585558887...
%o A306204 (PARI) t=1.0;for(i=1,500,p=2^i-1;if(isprime(p),t=t*(p+1)/p))
%Y A306204 Cf. A065446 (the corresponding product over all Mersenne numbers, prime or composite).
%Y A306204 Cf. A173898 (the sum of reciprocals of the Mersenne primes).
%Y A306204 Cf. A065442 (the sum of reciprocals of the Mersenne numbers, prime or composite).
%Y A306204 Cf. A046528.
%K A306204 nonn,cons
%O A306204 1,2
%A A306204 _Tomohiro Yamada_, Jan 29 2019