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 A244920 #42 May 26 2025 11:47:56
%S A244920 1,7,6,2,7,4,7,1,7,4,0,3,9,0,8,6,0,5,0,4,6,5,2,1,8,6,4,9,9,5,9,5,8,4,
%T A244920 6,1,8,0,5,6,3,2,0,6,5,6,5,2,3,2,7,0,8,2,1,5,0,6,5,9,1,2,1,7,3,0,6,7,
%U A244920 5,4,3,6,8,4,4,4,0,5,2,1,7,5,6,6,7,4,1,3,7,8,3,8,2,0,5,1,2,0,8,5,7
%N A244920 Decimal expansion of 2*log(1+sqrt(2)), the integral over the square [0,1]x[0,1] of 1/sqrt(x^2+y^2) dx dy.
%C A244920 Number field regulator of the cyclotomic number field Q(zeta_8), where zeta_8 = sqrt(i), an eighth root of 1. - _Alonso del Arte_, Mar 11 2017
%H A244920 G. C. Greubel, <a href="/A244920/b244920.txt">Table of n, a(n) for n = 1..10000</a>
%H A244920 D. H. Bailey, J. M. Borwein and R. E. Crandall, <a href="https://doi.org/10.1090/S0025-5718-10-02338-0">Advances in the theory of box integrals</a>, Math. Comp., Vol. 79, No. 271 (2010), pp. 1839-1866. See p. 1860.
%H A244920 LMFDB, <a href="http://www.lmfdb.org/NumberField/4.0.256.1">Global Number Field 4.0.256.1: Q(zeta_8)</a>.
%H A244920 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>
%F A244920 Equals 2*arcsinh(1).
%F A244920 Equals Integral_{x>=1} 1/(x*(1+x)^(1/2)) dx. - Pointed out by _Robert FERREOL_.
%F A244920 Equals arccosh(3). - _Vaclav Kotesovec_, Dec 11 2016
%F A244920 Equals Integral_{x>=1} arcsinh(x)/x^2 dx. - _Amiram Eldar_, Jun 26 2021
%F A244920 Equals Integral_{x = 0..Pi/2} x/cos(x/2) dx. - _Peter Bala_, Aug 13 2024
%F A244920 Equals log(A156035). - _Hugo Pfoertner_, Aug 17 2024
%F A244920 Equals arcsinh(2*sqrt(2)). - _Akiva Weinberger_, Dec 03 2024
%F A244920 Equals Integral_{x=0..oo} erf(sqrt(x))/(x*e^x) dx. - _Kritsada Moomuang_, May 25 2025
%e A244920 1.7627471740390860504652186499595846180563206565232708215065912173...
%t A244920 RealDigits[2 * Log[1 + Sqrt[2]], 10, 101] // First
%t A244920 RealDigits[NumberFieldRegulator[Sqrt[I]], 10, 100][[1]] (* _Alonso del Arte_, Mar 11 2017 *)
%o A244920 (PARI) 2*asinh(1) \\ _Michel Marcus_, Mar 18 2017
%Y A244920 Equals twice A091648. - _Michel Marcus_, Mar 18 2017
%Y A244920 Cf. A156035.
%K A244920 nonn,cons,easy
%O A244920 1,2
%A A244920 _Jean-François Alcover_, Jul 08 2014