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 A375151 #22 Aug 29 2025 13:40:00 %S A375151 1,4,6,1,9,0,2,2,0,0,0,8,1,5,4,3,6,2,6,1,1,6,3,7,7,2,0,6,6,8,3,1,4,5, %T A375151 8,5,1,9,3,6,7,5,2,8,3,0,7,5,9,4,6,2,2,4,0,8,5,5,3,1,8,4,9,3,1,7,7,6, %U A375151 7,2,5,8,1,3,9,9,6,7,5,9,0,4,9,1,9,6,2,7,7,9 %N A375151 Decimal expansion of the circumradius of a regular 9-gon with unit side length. %H A375151 Paolo Xausa, <a href="/A375151/b375151.txt">Table of n, a(n) for n = 1..10000</a> %H A375151 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RegularPolygon.html">Regular Polygon</a>. %H A375151 Wikipedia, <a href="https://en.wikipedia.org/wiki/Regular_polygon">Regular polygon</a>. %H A375151 <a href="/index/Al#algebraic_06">Index entries for algebraic numbers, degree 6</a>. %F A375151 Equals csc(Pi/9)/2 = A121602/2. %F A375151 Equals 1/(2*sin(Pi/9)) = 1/A272488. %F A375151 Equals A375152/cos(Pi/9) = A375152/A019879. %F A375151 Equals A375152 + A375153. %F A375151 Largest of the 6 real-valued roots of 3*x^6-9*x^4+6*x^2-1=0. - _R. J. Mathar_, Aug 29 2025 %e A375151 1.46190220008154362611637720668314585193675283... %t A375151 First[RealDigits[Csc[Pi/9]/2, 10, 100]] %o A375151 (PARI) .5/sin(Pi/9) \\ _Charles R Greathouse IV_, Feb 05 2025 %Y A375151 Cf. A375152 (apothem), A375153 (sagitta), A256853 (area). %Y A375151 Cf. circumradius of other polygons with unit side length: A020760 (triangle), A010503 (square), A300074 (pentagon), A374957 (heptagon), A285871 (octagon), A001622 (10-gon), A375190 (11-gon), A188887 (12-gon) %Y A375151 Cf. A019879, A121602, A272488. %K A375151 nonn,cons,easy,changed %O A375151 1,2 %A A375151 _Paolo Xausa_, Aug 01 2024