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 A274072 #18 Oct 21 2024 09:00:16
%S A274072 0,6,24,126,624,3126,15624,78126,390624,1953126,9765624,48828126,
%T A274072 244140624,1220703126,6103515624,30517578126,152587890624,
%U A274072 762939453126,3814697265624,19073486328126,95367431640624,476837158203126,2384185791015624,11920928955078126
%N A274072 a(n) = 5^n-(-1)^n.
%H A274072 Colin Barker, <a href="/A274072/b274072.txt">Table of n, a(n) for n = 0..1000</a>
%H A274072 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,5).
%F A274072 O.g.f.: 6*x/((1+x)*(1-5*x)).
%F A274072 E.g.f.: exp(5*x) - exp(-x).
%F A274072 a(n) = 4*a(n-1) + 5*a(n-2) for n>1.
%F A274072 a(n) = 6*A015531(n).
%t A274072 LinearRecurrence[{4, 5}, {0, 6}, 30] (* _Paolo Xausa_, Oct 21 2024 *)
%o A274072 (PARI) concat(0, Vec(6*x/((1+x)*(1-5*x)) + O(x^30)))
%Y A274072 Cf. A015531.
%Y A274072 Sequences of the type k^n-(-1)^n: A062157 (k=0), A010673 (k=1), A062510 (k=2), A105723 (k=3), A247281 (k=4), this sequence (k=5), A274073 (k=6).
%K A274072 nonn,easy
%O A274072 0,2
%A A274072 _Colin Barker_, Jun 09 2016