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 A236398 #28 Jul 18 2025 17:17:13 %S A236398 1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1, %T A236398 2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1, %U A236398 1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1,2,1,1,1 %N A236398 Period 4: repeat 1,1,2,1. %D A236398 H. Blaine Lawson, Jr. and M.-L. Michelsohn, Spin Geometry, Princeton, p. 33. %H A236398 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,1). %F A236398 a(n) = a(n-4) for n > 4. G.f.: x*(1 + x + 2*x^2 + x^3)/(1 - x^4). - _Chai Wah Wu_, Jun 04 2016 %F A236398 E.g.f.: (-2 - sin(x) + 3*sinh(x) + 2*cosh(x))/2. - _Ilya Gutkovskiy_, Jun 04 2016 %F A236398 a(n) = (5-cos(n*Pi)-2*sin(n*Pi/2))/4. - _Luce ETIENNE_, Feb 17 2017 %o A236398 (Magma) &cat [[1, 1, 2, 1]^^24]; // _Bruno Berselli_, Dec 10 2015 %o A236398 (PARI) a(n)=n=n%8; if(n==3||n==7, 2, 1) \\ _Charles R Greathouse IV_, Jul 17 2016 %Y A236398 Cf. A177704, A138191. %K A236398 nonn,easy %O A236398 1,3 %A A236398 _N. J. A. Sloane_, Jan 29 2014 %E A236398 Definition corrected by _Paul Curtz_. - _N. J. A. Sloane_, Oct 10 2016