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 A103901 #8 Feb 16 2025 08:32:56 %S A103901 3,7,31,127 %N A103901 Mersenne primes p such that M(p) = 2^p - 1 is also a (Mersenne) prime. %C A103901 Same as exponents of double Mersenne primes. Only four terms are known. %D A103901 R. K. Guy, Unsolved Problems in Number Theory, 3rd ed., Springer-Verlag, NY, 2004, Sec. A3. %D A103901 G. H. Hardy and E. M. Wright, An Introduction to the Theory of Numbers, 3rd ed., Oxford Univ. Press, 1954, p. 16. %D A103901 P. Ribenboim, The New Book of Prime Number Records, Springer-Verlag, NY, 1996, Chap. 2, Sec. VII. %H A103901 C. K. Caldwell, <a href="http://www.utm.edu/research/primes/mersenne/index.html#unknown">Mersenne Primes: Conjectures and Unsolved Problems</a> %H A103901 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DoubleMersenneNumber.html">Double Mersenne Number</a> %H A103901 Wikipedia, <a href="http://www.wikipedia.org/wiki/Mersenne_prime">Mersenne prime</a> %e A103901 2^2 - 1 = 3 and 2^3 - 1 = 7 are Mersenne primes, so 3 is a member. %Y A103901 Cf. A000043, A000668, A001348, A077586, A103902. %K A103901 nonn,more,hard %O A103901 1,1 %A A103901 _Jonathan Sondow_, Feb 20 2005