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 A152174 #24 Apr 09 2024 08:09:10
%S A152174 1,-4,12,-40,128,-416,1344,-4352,14080,-45568,147456,-477184,1544192,
%T A152174 -4997120,16171008,-52330496,169345024,-548012032,1773404160,
%U A152174 -5738856448,18571329536,-60098084864,194481487872,-629355315200
%N A152174 a(n) = -2*a(n-1)+4*a(n-2), n>1 ; a(0) = 1, a(1) = -4.
%C A152174 Signed version of A087206.
%H A152174 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (-2,4).
%F A152174 G.f.: (1-2x)/(1+2x-4x^2).
%F A152174 a(n) = Sum_{k=0..n} A147703(n,k)*(-5)^k.
%F A152174 a(n) = (-1)^n * A087206(n).
%t A152174 LinearRecurrence[{-2,4},{1,-4},30] (* _Harvey P. Dale_, Feb 13 2023 *)
%o A152174 (PARI) Vec((1-2*x)/(1+2*x-4*x^2)+O(x^99)) \\ _Charles R Greathouse IV_, Jan 11 2012
%Y A152174 Cf. A087206, A147703.
%K A152174 sign,easy
%O A152174 0,2
%A A152174 _Philippe Deléham_, Nov 27 2008