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 A155628 #21 Mar 02 2022 12:08:51
%S A155628 1,4,34,280,2146,15784,113554,807160,5699266,40091464,281426674,
%T A155628 1973132440,13824509986,96821901544,677954637394,4746487768120,
%U A155628 33228635602306,232613334118024,1628344878433714,11398620307466200
%N A155628 a(n) = 7^n-4^n+1^n.
%H A155628 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (12,-39,28).
%F A155628 G.f.: 1/(1-7*x)-1/(1-4*x)+1/(1-x). E.g.f.: e^(7*x)-e^(4*x)+e^x.
%F A155628 a(n) = 11*a(n-1)-28*a(n-2)+18 with a(0)=1, a(1)=4. - _Vincenzo Librandi_, Jul 21 2010
%t A155628 Table[7^n-4^n+1,{n,0,20}] (* or *) LinearRecurrence[{12,-39,28},{1,4,34},20] (* _Harvey P. Dale_, Jul 16 2017 *)
%o A155628 (PARI) a(n)=7^n-4^n+1 \\ _Charles R Greathouse IV_, Sep 24 2015
%Y A155628 Cf. A155596, A155597, A155598, A155599, A155600, A155601, A155622, A155623, A155624, A155625, A155626, A155627.
%K A155628 nonn,easy
%O A155628 0,2
%A A155628 _Mohammad K. Azarian_, Jan 30 2009