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 A280585 #24 Jun 06 2025 13:25:30 %S A280585 3,0,6,1,4,6,7,4,5,8,9,2,0,7,1,8,1,7,3,8,2,7,6,7,9,8,7,2,2,4,3,1,9,0, %T A280585 9,3,4,0,9,0,7,5,6,4,9,9,8,8,5,0,1,6,3,3,1,4,7,0,4,0,5,0,8,5,0,2,0,3, %U A280585 6,8,2,7,1,6,8,0,7,1,7,5,3,7,8,9,6,1,1,0,2,8,2,7,3,8,2,6,8,3,7,7,1,8,7,3,9 %N A280585 Decimal expansion of 8*sin(Pi/8). %C A280585 Decimal expansion of the ratio of the perimeter of a regular 8-gon (octagon) to its diameter (largest diagonal). %H A280585 <a href="/index/Al#algebraic_04">Index entries for algebraic numbers, degree 4</a>. %F A280585 Equals 8*A182168. %e A280585 3.061467458920718173827679872243190934090756499885016331470405085020368271... %p A280585 evalf(8*sin(Pi/8),100); # _Wesley Ivan Hurt_, Feb 01 2017 %t A280585 RealDigits[8*Sin[Pi/8], 10, 120][[1]] (* _Amiram Eldar_, Jun 26 2023 *) %o A280585 (PARI) 8*sin(Pi/8) %Y A280585 Cf. For other n-gons: A010466 (n=4), 10*A019827 (n=5, 10), A280533 (n=7), A280633 (n=9), A280725 (n=11), A280819 (n=12). %Y A280585 Cf. A182168. %K A280585 nonn,cons %O A280585 1,1 %A A280585 _Rick L. Shepherd_, Jan 05 2017