cp's OEIS Frontend

A343392 Decimal expansion of 2*Pi*sqrt(2).

%I A343392 #24 Aug 31 2024 12:39:03
%S A343392 8,8,8,5,7,6,5,8,7,6,3,1,6,7,3,2,4,9,4,0,3,1,7,6,1,9,8,0,1,2,1,3,8,7,
%T A343392 3,9,7,2,2,9,2,4,3,3,7,8,7,5,1,3,8,0,4,4,6,1,7,0,7,9,1,2,1,3,9,1,2,8,
%U A343392 6,9,5,8,6,1,9,8,9,4,7,8,2,1,1,5,0,6,5,3,8,6,9
%N A343392 Decimal expansion of 2*Pi*sqrt(2).
%C A343392 Circumference of the circumcircle of the square whose sides = 2.
%C A343392 Hypotenuse of the right isosceles triangle with the two legs = 2*Pi.
%C A343392 Perimeter of the closed curve with implicit Cartesian equation x^2 + y^2 = abs(x) + abs(y). This curve in the first quadrant is the half-circle with equation (x-1/2)^2 + (y-1/2)^2 = 1/2, hence, the curve is the union of 4 identical half-circles with diameter = sqrt(2) obtained by symmetries. (See link Curve.)
%C A343392 S. Ramanujan produced a curious approximation to 2*Pi*sqrt(2) by dividing 99^2 by 1103 (see link Prime Curios! and A343393).
%D A343392 David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987. See p. 54.
%H A343392 Chris K. Caldwell and G. L. Honaker, Jr., <a href="https://primes.utm.edu/curios/page.php?short=1103">1103, 1st comment</a>, Prime Curios!
%H A343392 Bernard Schott, <a href="/A343392/a343392.jpg">Curve x^2+y^2 = abs(x)+abs(y)</a>.
%H A343392 <a href="/index/Cu#curves">Index to sequences related to curves</a>.
%H A343392 <a href="/index/Tra#transcendental">Index entries for transcendental numbers</a>.
%F A343392 2*Pi*sqrt(2) = A019692 * A002193 = A010466 * A000796 = 2 * A063448.
%e A343392 8.88576587631673249403176198012138739722924337875138044617
%p A343392 evalf(2*Pi*sqrt(2),120);
%t A343392 RealDigits[2*Sqrt[2]*Pi, 10, 100][[1]] (* _Amiram Eldar_, Apr 13 2021 *)
%Y A343392 Cf. A000796, A002193, A010466, A019692, A063448, A343393.
%K A343392 nonn,cons
%O A343392 1,1
%A A343392 _Bernard Schott_, Apr 13 2021