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 A105533 #36 May 27 2025 14:53:56 %S A105533 1,4,1,8,9,7,0,5,4,6,0,4,1,6,3,9,2,2,8,1,2,8,5,1,6,1,7,1,0,2,5,5,3,0, %T A105533 8,3,0,0,7,7,8,1,7,5,8,7,2,8,4,6,4,0,7,2,3,7,8,1,3,0,0,2,9,3,6,3,4,4, %U A105533 1,6,2,6,7,5,9,9,3,1,1,6,0,9,4,4,1,9,1,8,6,1,6,3,4,2,4,6,5,1,8,1,1,7,5,2,2 %N A105533 Decimal expansion of arctan(1/7). %H A105533 D. H. Lehmer, <a href="https://web.archive.org/web/20240224193146/https://www.maa.org/sites/default/files/pdf/pubs/amm_supplements/Monthly_Reference_7.pdf">On Arccotangent Relations for π</a>, The American Mathematical Monthly, Vol. 45, No. 10 (Dec., 1938), pp. 657-664. %H A105533 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Machin-LikeFormulas.html">Machin-Like Formulas</a>. %H A105533 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a> %F A105533 2*A073000 - arctan(1/7) = 2*A105531 + arctan(1/7) = Pi/4. %F A105533 5*arctan(1/7) + 2*arctan(3/79) = Pi/4. - _Frank Ellermann_, Mar 01 2020 %F A105533 Equals arcsin(1/(5*sqrt(2))) = arccos(7/(5*sqrt(2))). - _Amiram Eldar_, Jul 11 2023 %e A105533 0.1418970546041639228128516171... %t A105533 RealDigits[ArcTan[1/7],10,120][[1]] (* _Harvey P. Dale_, Oct 03 2012 *) %o A105533 (PARI) atan(1/7) \\ _Michel Marcus_, Mar 01 2020 %Y A105533 Cf. A073000, A105531. %K A105533 cons,nonn %O A105533 0,2 %A A105533 Bryan Jacobs (bryanjj(AT)gmail.com), Apr 12 2005