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 A139305 #7 Jul 10 2025 15:59:49 %S A139305 0,255,72057594037927935, %T A139305 452312848583266388373324160190187140051835877600158453279131187530910662655 %N A139305 a(n) = (2^(2p - 1)/32)-1, where p is the n-th Mersenne prime A000668(n). %C A139305 Next term is too large to list here. %F A139305 a(n) = (2^(2*A000668(n)-1)/32)-1 = (A139294(n)/32)-1. %t A139305 a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 8) - 1; Array[a, 4] (* _Amiram Eldar_, Jul 10 2025 *) %Y A139305 Cf. A000668, A139286, A139294, A139295, A139296, A139297, A139298, A139299, A139300, A139301, A139302, A139303, A139304, A139306. %K A139305 nonn %O A139305 1,2 %A A139305 _Omar E. Pol_, Apr 13 2008 %E A139305 Edited by _Max Alekseyev_, Apr 23 2010