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 A220425 #32 Aug 10 2018 04:20:10
%S A220425 1,5,12,23,40,67,112,191,336,611,1144,2191,4264,8387,16608,33023,
%T A220425 65824,131395,262504,524687,1049016,2097635,4194832,8389183,16777840,
%U A220425 33555107,67109592,134218511,268436296,536871811,1073742784,2147484671,4294968384,8589935747
%N A220425 a(n) = n^2 + 2*n + 2^n.
%H A220425 Iain Fox, <a href="/A220425/b220425.txt">Table of n, a(n) for n = 0..3321</a>
%H A220425 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (5,-9,7,-2).
%F A220425 G.f.: (x^3-4*x^2+1) / ((x-1)^3*(2*x-1)). - _Colin Barker_, May 09 2013
%F A220425 E.g.f.: exp(x) * (exp(x) + x*(3 + x)). - _Iain Fox_, Aug 08 2018
%t A220425 Table[n^2 + 2*n + 2^n, {n, 0, 50}] (* _T. D. Noe_, Dec 14 2012 *)
%o A220425 (Maxima) makelist(n^2+2*n+2^n, n, 0, 20); /* _Martin Ettl_, Dec 15 2012 */
%o A220425 (PARI) a(n)=n^2+2*n+2^n \\ _Charles R Greathouse IV_, Oct 07 2015
%o A220425 (PARI) first(n) = Vec((1 - 4*x^2 + x^3)/((1 - x)^3 * (1 - 2*x)) + O(x^n)) \\ _Iain Fox_, Aug 08 2018
%K A220425 nonn,easy
%O A220425 0,2
%A A220425 _Dario Piazzalunga_, Dec 14 2012