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 A275277 #8 Apr 09 2022 13:29:04
%S A275277 1,1,1,1,8,15,43,113,295,778,2045,5377,14141,37185,97784,257139,
%T A275277 676187,1778141,4675903,12296026,32334345,85028273,223595289,
%U A275277 587979169,1546184200,4065935847,10692021243,28116360553,73936416023,194427497258,511277848229
%N A275277 a(n) = a(n-1) + 3*a(n-2) + 3*a(n-3) + a(n-4), where a(0) = a(1) = a(2) = a(3) = 1.
%H A275277 Clark Kimberling, <a href="/A275277/b275277.txt">Table of n, a(n) for n = 0..1000</a>
%H A275277 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,3,3,1).
%F A275277 a(n) = a(n-1) + 3*a(n-2) + 3*a(n-3) + a(n-4), where a(0) = a(1) = a(2) = a(3) = 1.
%F A275277 G.f.: (-1 + 3 x^2 + 6 x^3)/(-1 + x + 3 x^2 + 3 x^3 + x^4).
%t A275277 LinearRecurrence[{1, 3, 3, 1}, {1, 1, 1, 1}, 50]
%t A275277 RecurrenceTable[{a[0]==a[1]==a[2]==a[3]==1,a[n]==a[n-1]+3a[n-2]+ 3a[n-3]+ a[n-4]},a,{n,30}] (* _Harvey P. Dale_, Apr 09 2022 *)
%Y A275277 Cf. A099234.
%K A275277 nonn,easy
%O A275277 0,5
%A A275277 _Clark Kimberling_, Aug 11 2016