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 A279230 #14 Apr 07 2019 09:06:14
%S A279230 1,4,9,14,15,8,-7,-22,-21,12,77,142,143,16,-239,-494,-493,20,1045,
%T A279230 2070,2071,24,-4071,-8166,-8165,28,16413,32798,32799,32,-65503,
%U A279230 -131038,-131037,36,262181,524326,524327,40,-1048535,-2097110,-2097109,44,4194349,8388654,8388655
%N A279230 Expansion of 1/((1-x)^2*(1-2*x+2*x^2)).
%C A279230 Partial sums of A077860.
%H A279230 Colin Barker, <a href="/A279230/b279230.txt">Table of n, a(n) for n = 0..1000</a>
%H A279230 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-7,6,-2).
%F A279230 a(n) = 4*a(n-1) - 7*a(n-2) + 6*a(n-3) - 2*a(n-4) for n>3.
%F A279230 a(n) = 2*a(n-1) - 2*a(n-2) + n + 1, with a(-1) = a(-2) = 0.
%F A279230 a(n) = (3 - (1-i)^(1+n) - (1+i)^(1+n) + n) where i=sqrt(-1). - _Colin Barker_, Aug 04 2017
%F A279230 From _Seiichi Manyama_, Apr 07 2019: (Start)
%F A279230 a(n) = Sum_{k=0..floor(n/2)} (-1)^k*binomial(n+3,2*k+3).
%F A279230 a(n) = Sum_{i=0..n} Sum_{j=0..n-i} (-1)^j * binomial(i+1,j+1) * binomial(n-i+1,j+1). (End)
%o A279230 (PARI) Vec(1 / ((1 - x)^2*(1 - 2*x + 2*x^2)) + O(x^50)) \\ _Colin Barker_, Aug 04 2017
%o A279230 (PARI) {a(n) = sum(k=0, n\2, (-1)^k*binomial(n+3, 2*k+3))} \\ _Seiichi Manyama_, Apr 07 2019
%Y A279230 Cf. A001477, A045618, A077859, A077860, A279231.
%K A279230 sign,easy
%O A279230 0,2
%A A279230 _Philippe Deléham_, Dec 08 2016