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 A117191 #15 Feb 16 2025 08:33:00
%S A117191 1,5,5,4,6,8,2,2,7,5,4,8,2,1,0,0,0,8,9,8,7,0,2,3,2,0,8,0,7,8,2,8,0,4,
%T A117191 0,0,2,0,6,0,4,4,7,3,0,6,2,6,5,6,6,1,3,7,9,0,9,8,9,2,0,2,0,4,3,3,2,8,
%U A117191 7,7,9,4,1,5,2,9,3,2,8,0,5,3,6,5,1,1,3,9,7,6,3,8,2,3,1,8,7,4,8,9,3,6,3,0,5
%N A117191 Decimal expansion of 4^(1/Pi).
%C A117191 Gosper found that lim[n approaches infinity] Prod[i=n..2n] Pi/2 arctan i = 4^(1/Pi) ~ 1.554682275...
%D A117191 Gosper, R. W. math-fun(AT)cs.arizona.edu posting, Sept. 1996.
%D A117191 Gosper, R. W. "a product." math-fun(AT)cs.arizona.edu posting, Sept. 27, 1996.
%H A117191 R. W. Gosper, <a href="http://www.tweedledum.com/rwg/idents.htm">Some identities</a>
%H A117191 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PiFormulas.html">Pi Formulas</a>.
%e A117191 1.5546822754821000898702320807828040020604473062656613790989...
%t A117191 RealDigits[4^(1/Pi),10,120][[1]] (* _Harvey P. Dale_, Sep 05 2019 *)
%o A117191 (Macsyma) 'limit(funmake_no_simp(".",[%pi/2/atan(n),%pi/2/atan(n+1),"","",%pi/2/atan(2*n)]),n,inf)=4^(1/%pi)
%K A117191 cons,easy,nonn
%O A117191 1,2
%A A117191 _Jonathan Vos Post_, Apr 21 2006
%E A117191 More terms from _Eric W. Weisstein_, May 01 2006
%E A117191 Edited by _N. J. A. Sloane_, Jul 01 2008 at the suggestion of _R. J. Mathar_