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 A017819 #37 Apr 21 2025 13:22:41
%S A017819 1,0,0,1,1,1,2,2,3,5,6,8,12,16,22,31,42,58,81,111,153,212,292,403,557,
%T A017819 768,1060,1464,2020,2788,3849,5312,7332,10121,13969,19281,26614,36734,
%U A017819 50703,69985,96598,133332,184036,254020,350618,483951,667986,922006,1272625,1756575,2424561,3346568,4619192,6375767,8800329,12146896
%N A017819 Expansion of 1/(1-x^3-x^4-x^5-x^6).
%C A017819 Number of compositions of n into parts 3, 4, 5, and 6. - _David Neil McGrath_, Aug 17 2014
%H A017819 Vincenzo Librandi, <a href="/A017819/b017819.txt">Table of n, a(n) for n = 0..1000</a>
%H A017819 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,1,1,1,1).
%F A017819 a(n) = a(n-6) + a(n-5) + a(n-4) + a(n-3). - _Jon E. Schoenfield_, Aug 07 2006
%F A017819 a(n) = a(n-1) + a(n-4) + {1, -1, or 0} depending on whether n mod 3 is {0, 1, or 2}. - _Barry Cipra_, Mar 03 2008
%t A017819 CoefficientList[Series[1 / (1 - Total[x^Range[3, 6]]), {x, 0, 50}], x] (* _Vincenzo Librandi_, Jun 27 2013 *)
%t A017819 LinearRecurrence[{0,0,1,1,1,1},{1,0,0,1,1,1},50] (* _Harvey P. Dale_, Aug 15 2014 *)
%o A017819 (Magma) m:=50; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(1/((1-x^3-x^4-x^5-x^6)))); // _Vincenzo Librandi_, Jun 27 2013
%o A017819 (Magma) I:=[1,0,0,1,1,1]; [n le 6 select I[n] else Self(n-3)+Self(n-4)+Self(n-5)+Self(n-6): n in [1..50]]; // _Vincenzo Librandi_, Jun 27 2013
%o A017819 (PARI) Vec(1/(1-x^3-x^4-x^5-x^6)+ O(x^60)) \\ _Michel Marcus_, Aug 17 2014
%Y A017819 Cf. A137200.
%K A017819 nonn,easy
%O A017819 0,7
%A A017819 _N. J. A. Sloane_