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 A139301 #8 Jul 10 2025 16:01:01 %S A139301 3,1023,288230376151711743, %T A139301 1809251394333065553493296640760748560207343510400633813116524750123642650623 %N A139301 a(n) = (2^(2p - 1)/8)-1, where p is the n-th Mersenne prime A000668(n). %F A139301 a(n) = (2^(2*A000668(n)-1)/8)-1 = (A139294(n)/8)-1. %t A139301 a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 6) - 1; Array[a, 4] (* _Amiram Eldar_, Jul 10 2025 *) %Y A139301 Cf. A000668, A139294, A139295, A139296, A139297, A139298, A139299, A139300, A139302, A139303, A139304, A139305, A139306. %K A139301 nonn %O A139301 1,1 %A A139301 _Omar E. Pol_, Apr 13 2008 %E A139301 a(4) from _Amiram Eldar_, Jul 10 2025