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 A027656 #61 Dec 30 2023 23:44:17
%S A027656 1,0,2,0,3,0,4,0,5,0,6,0,7,0,8,0,9,0,10,0,11,0,12,0,13,0,14,0,15,0,16,
%T A027656 0,17,0,18,0,19,0,20,0,21,0,22,0,23,0,24,0,25,0,26,0,27,0,28,0,29,0,
%U A027656 30,0,31,0,32,0,33,0,34,0,35,0,36,0,37,0,38,0,39,0,40,0,41,0,42,0,43,0
%N A027656 Expansion of 1/(1-x^2)^2 (included only for completeness - the policy is always to omit the zeros from such sequences).
%C A027656 a(n) is the number of nonnegative integer solutions to the equation x+y+z=n such that x+y=z. - _Geoffrey Critzer_, Jul 12 2013
%H A027656 G. C. Greubel, <a href="/A027656/b027656.txt">Table of n, a(n) for n = 0..5000</a>
%H A027656 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,0,-1)
%F A027656 From _Paul Barry_, May 27 2003: (Start)
%F A027656 Binomial transform is A045891. Partial sums are A008805. The sequence 0, 1, 0, 2, ... has a(n)=floor((n+2)/2)(1-(-1)^n)/2.
%F A027656 a(n) = floor((n+3)/2) * (1+(-1)^n)/2. (End)
%F A027656 a(n) = (n+2)(n+3)/2 mod n+2. - _Amarnath Murthy_, Jun 17 2004
%F A027656 a(n) = (n+2)*(1 + (-1)^n)/4. - _Bruno Berselli_, Apr 01 2011
%F A027656 a(n) = A008619(n) * A059841(n). - _Wesley Ivan Hurt_, Jun 17 2013
%F A027656 E.g.f.: cosh(x) + x*sinh(x)/2. - _Stefano Spezia_, Mar 26 2022
%t A027656 CoefficientList[Series[1/(1-x^2)^2,{x,0,100}],x] (* _Geoffrey Critzer_, Jul 12 2013 *)
%o A027656 (Magma) [(n+2)*(1+(-1)^n)/4: n in [0..75]]; // _Vincenzo Librandi_, Apr 02 2011
%o A027656 (PARI) a(n)=if(n%2,0,n/2+1) \\ _Charles R Greathouse IV_, Jan 18 2012
%o A027656 (SageMath) [(n+2)*((n+1)%2)/2 for n in (0..80)] # _G. C. Greubel_, Aug 01 2022
%Y A027656 Cf. A008619, A008805, A045891, A059841, A142150.
%K A027656 nonn,easy
%O A027656 0,3
%A A027656 _N. J. A. Sloane_