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 A055802 #28 Sep 08 2022 08:45:01
%S A055802 1,1,1,2,3,4,6,7,10,11,15,16,21,22,28,29,36,37,45,46,55,56,66,67,78,
%T A055802 79,91,92,105,106,120,121,136,137,153,154,171,172,190,191,210,211,231,
%U A055802 232,253,254,276,277,300,301,325,326,351,352,378,379,406,407,435
%N A055802 a(n) = T(n,n-2), array T as in A055801.
%C A055802 For n>2, a(n)+a(n+1) seems to be A002620(n+1)+1.
%H A055802 Colin Barker, <a href="/A055802/b055802.txt">Table of n, a(n) for n = 2..1000</a>
%H A055802 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A055802 G.f.: x^2*(1 -2*x^2 +x^3 +2*x^4 -x^5)/((1-x)^3*(1+x)^2).
%F A055802 a(n) = A114220(n-1), n>=3. - _R. J. Mathar_, Feb 03 2013
%F A055802 From _Colin Barker_, Jan 27 2016: (Start)
%F A055802 a(n) = (2*n^2 +2*(-1)^n*n -6*n -11*(-1)^n +11)/16 for n>2.
%F A055802 a(n) = (n^2 - 2*n)/8 for n>2 and even.
%F A055802 a(n) = (n^2 - 4*n + 11)/8 for n odd. (End)
%F A055802 E.g.f.: (4*x*(x-2) + x*(x-3)*cosh(x) + (x^2 -x +11)*sinh(x))/8. - _G. C. Greubel_, Jan 23 2020
%p A055802 seq( `if`(n==2, 1, (2*n^2 -6*n +11 +(-1)^n*(2*n -11))/16), n=2..65); # _G. C. Greubel_, Jan 23 2020
%t A055802 CoefficientList[Series[(1 -2*x^2 +x^3 +2*x^4 -x^5)/((1-x)^3*(1+x)^2), {x,0,65}], x] (* _Wesley Ivan Hurt_, Jan 20 2017 *)
%t A055802 Table[If[n==2,1, (2*n^2 -6*n +11 +(-1)^n*(2*n -11))/16], {n,2,65}] (* _G. C. Greubel_, Jan 23 2020 *)
%o A055802 (PARI) Vec(x^2*(1-2*x^2+x^3+2*x^4-x^5)/((1-x)^3*(1+x)^2) + O(x^65)) \\ _Charles R Greathouse IV_, Feb 03 2013
%o A055802 (PARI) vector(65, n, my(m=n+1); if(m==2, 1, (2*m^2 -6*m +11 +(-1)^m*(2*m -11))/16)) \\ _G. C. Greubel_, Jan 23 2020
%o A055802 (Magma) [1] cat [(2*n^2 -6*n +11 +(-1)^n*(2*n -11))/16: n in [3..65]]; // _G. C. Greubel_, Jan 23 2020
%o A055802 (Sage) [1]+[(2*n^2 -6*n +11 +(-1)^n*(2*n -11))/16 for n in (3..65)] # _G. C. Greubel_, Jan 23 2020
%o A055802 (GAP) Concatenation([1], List([3..65], n-> (2*n^2 -6*n +11 +(-1)^n*(2*n -11))/16 )); # _G. C. Greubel_, Jan 23 2020
%Y A055802 Cf. A002620, A134519.
%Y A055802 Cf. A055801, A055803, A055804, A055805, A055806.
%K A055802 nonn,easy
%O A055802 2,4
%A A055802 _Clark Kimberling_, May 28 2000