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 A037582 #24 Feb 17 2024 10:30:34
%S A037582 1,13,131,1313,13131,131313,1313131,13131313,131313131,1313131313,
%T A037582 13131313131,131313131313,1313131313131,13131313131313,
%U A037582 131313131313131,1313131313131313,13131313131313131,131313131313131313,1313131313131313131,13131313131313131313
%N A037582 Decimal expansion of a(n) is given by the first n terms of the periodic sequence with initial period 1,3.
%H A037582 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (10,1,-10).
%F A037582 G.f.: x*(1+3*x) / ( (x-1)*(10*x-1)*(1+x) ). - _R. J. Mathar_, Aug 12 2013
%t A037582 Table[FromDigits[PadRight[{},n,{1,3}]],{n,20}] (* _Harvey P. Dale_, Feb 11 2015 *)
%o A037582 (PARI) Vec(x*(1+3*x)/((x-1)*(10*x-1)*(1+x)) + O(x^25)) \\ _Jinyuan Wang_, Apr 14 2020
%Y A037582 Cf. A156641 (even bisection).
%K A037582 nonn,base,easy
%O A037582 1,2
%A A037582 _Clark Kimberling_
%E A037582 More terms from _Harvey P. Dale_, Feb 11 2015