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 A322851 #27 Feb 25 2019 21:00:57 %S A322851 1,1,3,6,15,49,255,2544,65535,6479346,4294967295,41981937869755, %T A322851 18446744073709551615,1762483107300123635910219390, %U A322851 340282366920938463463374607431768211455 %N A322851 a(n) = floor(2^(2^(n/2))-1). %C A322851 A051179 is a bisection of this sequence. %t A322851 Array[Floor[2^(2^(#/2)) - 1] &, 15, 0] (* _Michael De Vlieger_, Jan 04 2019 *) %o A322851 (PARI) a(n) = floor(2^(2^(n/2)))-1; \\ _Michel Marcus_, Jan 15 2019 %Y A322851 Cf. A051179. A322852 is the base-e analog. %K A322851 nonn,easy %O A322851 0,3 %A A322851 _Greg Huber_, Dec 28 2018