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 A021017 #34 Aug 05 2025 13:26:57
%S A021017 0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,
%T A021017 2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,
%U A021017 6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6,9,2,3,0,7,6
%N A021017 Decimal expansion of 1/13.
%C A021017 In 1741, Euler recognized that 10 times this number is close to (2^i + 2^(-i))/2, see Nahin (1988) and A219705. - _Alonso del Arte_, Nov 25 2012
%C A021017 Also decimal expansion of Sum_{i>=1} 1/14^i. - _Bruno Berselli_, Jan 03 2014
%D A021017 Florian Cajori, A History of Mathematical Notations, Dover edition (2012), par. 309.
%D A021017 Paul J. Nahin, An Imaginary Tale: The Story of sqrt(-1). Princeton, New Jersey: Princeton University Press (1988): 143.
%H A021017 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,-1,1).
%F A021017 From _Colin Barker_, Aug 15 2012: (Start)
%F A021017 a(n) = a(n - 1) - a(n - 3) + a(n - 4).
%F A021017 G.f.: -x*(3*x^2 - x + 7)/((x - 1)*(x + 1)*(x^2 - x + 1)). (End)
%F A021017 E.g.f.: (8*cosh(x) - 4*exp(x/2)*(2*cos(sqrt(3)*x/2) - sqrt(3)*sin(sqrt(3)*x/2)) + 19*sinh(x))/3. - _Stefano Spezia_, Aug 05 2025
%e A021017 0.076923076923076923076923076923076923076923...
%t A021017 LinearRecurrence[{1, 0, -1, 1}, {0, 7, 6, 9}, 98] (* with C. Barker's formula, _Peter Luschny_, Aug 15 2012 *)
%t A021017 Join[{0},RealDigits[1/13,10,120][[1]]] (* or *) PadRight[{},120,{0,7,6,9,2,3}] (* _Harvey P. Dale_, Dec 17 2017 *)
%Y A021017 Cf. A219705.
%K A021017 nonn,cons,easy
%O A021017 0,2
%A A021017 _N. J. A. Sloane_