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 A120669 #5 Dec 15 2014 14:47:43 %S A120669 1,3,8,0,2,1,4,1,8,2,7,4,9,0,7,9,9,0,4,0,0,8,7,5,5,8,1,8,1,4,1,7,0,1, %T A120669 4,4,0,1,3,9,6,6,6,1,9,9,4,0,0,1,0,2,1,7,4,0,7,6,9,3,1,2,2,7,9,6,9,6, %U A120669 4,0,3,9,1,1,0,0,9,2,6,8,1,7,8,1,4,1,0,5,7,5,5,1,7,0,3,8,5,0,0,8,9,7,6,3,5 %N A120669 Decimal expansion of arccos(1-8/(Pi^2)). %C A120669 For a circle with radius r, the measurement in radians of the central angle with endpoints on the circle that are r*4/Pi apart: The average central angle (<= Pi) formed using two randomly chosen points on a circle. The average arc length between such endpoints is r*A120669 corresponding to the average chord length r*A088538; so for the unit circle arc length is A120669 and chord length is A088538. %e A120669 1.38021418274907990400875581814... %t A120669 RealDigits[ArcCos[1-8/Pi^2],10,120][[1]] (* _Harvey P. Dale_, Dec 15 2014 *) %o A120669 (PARI) acos(1-8/Pi^2) %Y A120669 Cf. A088538, A120670 (same in degrees), A120671 (A120669/2Pi). %K A120669 cons,nonn %O A120669 1,2 %A A120669 _Rick L. Shepherd_, Jun 22 2006