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 A375068 #17 Feb 04 2025 15:20:25 %S A375068 1,6,2,4,5,9,8,4,8,1,1,6,4,5,3,1,6,3,0,7,7,9,3,5,7,0,6,1,0,7,5,6,7,2, %T A375068 3,2,4,7,7,4,5,1,7,3,5,7,6,0,7,3,7,5,5,0,1,5,3,9,0,2,3,5,9,5,6,8,3,3, %U A375068 6,4,5,0,4,8,0,3,7,2,4,7,4,1,6,1,3,4,3,8,6,7 %N A375068 Decimal expansion of the sagitta of a regular pentagon with unit side length. %H A375068 Paolo Xausa, <a href="/A375068/b375068.txt">Table of n, a(n) for n = 0..10000</a> %H A375068 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RegularPolygon.html">Regular Polygon</a>. %H A375068 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Sagitta.html">Sagitta</a> %H A375068 <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>. %F A375068 Equals tan(Pi/10)/2 = sqrt(1-2/sqrt(5))/2 = A019916/2. %F A375068 Equals A300074 - A375067. %F A375068 Equals A179050/5 = sqrt(A229760)/10. - _Hugo Pfoertner_, Jul 30 2024 %e A375068 0.1624598481164531630779357061075672324774517357607... %t A375068 First[RealDigits[Tan[Pi/10]/2, 10, 100]] %o A375068 (PARI) tan(Pi/10)/2 \\ _Charles R Greathouse IV_, Feb 04 2025 %o A375068 (PARI) polrootsreal(80*x^4-40*x^2+1)[3] \\ _Charles R Greathouse IV_, Feb 04 2025 %Y A375068 Cf. A300074 (circumradius), A375067 (apothem), A102771 (area). %Y A375068 Cf. sagitta of other polygons with unit side length: A020769 (triangle), A174968 (square), A375069 (hexagon), A374972 (heptagon), A375070 (octagon), A375153 (9-gon), A375189 (10-gon), A375192 (11-gon), A375194 (12-gon). %Y A375068 Cf. A019916, A179050, A229760. %K A375068 nonn,cons,easy %O A375068 0,2 %A A375068 _Paolo Xausa_, Jul 29 2024