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 A139299 #10 Jul 10 2025 16:02:02 %S A139299 7,2047,576460752303423487, %T A139299 3618502788666131106986593281521497120414687020801267626233049500247285301247 %N A139299 a(n) = 2^(2p - 1)/4-1, where p is the n-th Mersenne prime A000668(n). %F A139299 a(n) = 2^(2*A000668(n)-1)/4-1 = A139294(n)/4-1 = A139298(n)-1. %t A139299 a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 5) - 1; Array[a, 4] (* _Amiram Eldar_, Jul 10 2025 *) %Y A139299 Cf. A000668, A139294, A139295, A139296, A139297, A139298, A139300, A139301, A139302, A139303, A139304, A139305, A139306. %K A139299 nonn %O A139299 1,1 %A A139299 _Omar E. Pol_, Apr 13 2008 %E A139299 a(4) from _Amiram Eldar_, Jul 10 2025