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 A220588 #29 Aug 16 2017 17:13:47
%S A220588 1,0,-2,-4,-4,2,22,72,184,422,914,1916,3940,8010,16174,32528,65264,
%T A220588 130766,261802,523908,1048156,2096690,4193798,8388056,16776616,
%U A220588 33553782,67108162,134216972,268434644,536870042,1073740894,2147482656,4294966240,8589933470,17179867994
%N A220588 a(n) = 2^n - n^2 - n.
%H A220588 Colin Barker, <a href="/A220588/b220588.txt">Table of n, a(n) for n = 0..1000</a>
%H A220588 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (5,-9,7,-2).
%F A220588 a(n) = 2*a(n - 1) + ((n - 3)^2 + 3(n - 3)) = 2*a(n - 1) + A028552(n - 3) for n > 4.
%F A220588 a(n) = (2*a(n-1) + 7*a(n-2))*2 = A015519/2 for n > 4.
%F A220588 From _Colin Barker_, Aug 16 2017: (Start)
%F A220588 G.f.: (1 - 5*x + 7*x^2 - x^3) / ((1 - x)^3*(1 - 2*x)).
%F A220588 a(n) = 5*a(n-1) - 9*a(n-2) + 7*a(n-3) - 2*a(n-4) for n>3.
%F A220588 (End)
%e A220588 a(3) = -4 because 2^3 - 3^2 - 3 = 8 - 9 - 3 = -4.
%e A220588 a(4) = -4 because 2^4 - 4^2 - 4 = 16 - 16 - 4 = -4.
%e A220588 a(5) = 2 because 2^5 - 5^2 - 5 = 32 - 25 - 5 = 2.
%e A220588 a(6) = 22 because 2^6 - 6^2 - 6 = 64 - 36 - 6 = 22.
%t A220588 Table[2^n - n^2 - n, {n, 0, 32}] (* _Alonso del Arte_, Dec 16 2012 *)
%o A220588 (Maxima) A220588(n):=2^n-n^2-n$ makelist(A220588(n),n,0,20); /* _Martin Ettl_, Dec 18 2012 */
%o A220588 (PARI) Vec((1 - 5*x + 7*x^2 - x^3) / ((1 - x)^3*(1 - 2*x)) + O(x^40)) \\ _Colin Barker_, Aug 16 2017
%Y A220588 Cf. A015519, A024012, A001580.
%K A220588 sign,easy
%O A220588 0,3
%A A220588 _Dario Piazzalunga_, Dec 16 2012
%E A220588 a(3) corrected by _Charles A. Dagino_, Aug 16 2017