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 A139295 #11 Jul 10 2025 16:02:48 %S A139295 31,8191,2305843009213693951, %T A139295 14474011154664524427946373126085988481658748083205070504932198000989141204991 %N A139295 a(n) = 2^(2p - 1)-1, where p is the n-th Mersenne prime A000668(n). %F A139295 a(n) = 2^(2*A000668(n)-1)-1 = A139294(n)-1. %t A139295 a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 3) - 1; Array[a, 4] (* _Amiram Eldar_, Jul 10 2025 *) %Y A139295 Cf. A000668, A139294, A139296, A139297, A139298, A139299, A139300, A139301, A139302, A139303, A139304, A139305, A139306. %K A139295 nonn %O A139295 1,1 %A A139295 _Omar E. Pol_, Apr 13 2008