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 A139303 #8 Jul 10 2025 16:00:43 %S A139303 1,511,144115188075855871, %T A139303 904625697166532776746648320380374280103671755200316906558262375061821325311 %N A139303 a(n) = (2^(2p - 1)/16)-1, where p is the n-th Mersenne prime A000668(n). %F A139303 a(n) = (2^(2*A000668(n)-1)/16)-1 = (A139294(n)/16)-1. %t A139303 a[n_] := 2^(2^(MersennePrimeExponent[n] + 1) - 7) - 1; Array[a, 4] (* _Amiram Eldar_, Jul 10 2025 *) %Y A139303 Cf. A000668, A139294, A139295, A139296, A139297, A139298, A139299, A139300, A139301, A139302, A139304, A139305, A139306. %K A139303 nonn %O A139303 1,2 %A A139303 _Omar E. Pol_, Apr 13 2008 %E A139303 a(4) from _Amiram Eldar_, Jul 10 2025