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 A063820 #6 Jun 13 2019 11:22:23 %S A063820 1,40,1560,60840,2372760,92537640,3608967960,140749750440, %T A063820 5489240267160,214080370419240,8349134446350360,325616243407664040, %U A063820 12699033492898897560,495262306223057004840,19315229942699223188760,753293967765269704361640 %N A063820 Growth series for fundamental group of orientable closed surface of genus 10. %D A063820 P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 160, Sigma(Gamma_10, S_10; z). %H A063820 Colin Barker, <a href="/A063820/b063820.txt">Table of n, a(n) for n = 0..600</a> %H A063820 <a href="/index/Rec#order_21">Index entries for linear recurrences with constant coefficients</a>, signature (39,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-39,1). %F A063820 G.f.: (1+x)*(1-x^20)/(1-39*x+39*x^20-x^21). %o A063820 (PARI) Vec((1+x)*(1-x^20)/(1-39*x+39*x^20-x^21) + O(x^15)) \\ _Colin Barker_, Jun 13 2019 %K A063820 easy,nonn %O A063820 0,2 %A A063820 _N. J. A. Sloane_, Aug 21 2001