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%I #22 Jan 08 2023 13:02:18
%S 0,1,3,4,7,13,24,44,81,149,274,504,927,1705,3136,5768,10609,19513,
%T 35890,66012,121415,223317,410744,755476,1389537,2555757,4700770,
%U 8646064,15902591,29249425,53798080,98950096,181997601,334745777,615693474
%N Satisfies the tribonacci recurrence: a(n) = a(n-1) + a(n-2) + a(n-3).
%H Vincenzo Librandi, <a href="/A282718/b282718.txt">Table of n, a(n) for n = 0..1000</a>
%H Julien Leroy, Michel Rigo, Manon Stipulanti, <a href="http://dx.doi.org/10.1016/j.disc.2017.01.003">Counting the number of non-zero coefficients in rows of generalized Pascal triangles</a> Discrete Mathematics 340 (2017), 862-881. See Example 43.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,1).
%F a(n) = A000073(n+2), n >= 3. - _R. J. Mathar_, Mar 03 2017
%F G.f.: x*(1 + 2*x - x^3 - x^4)/(1 - x - x^2 - x^3). - _Bruno Berselli_, Mar 03 2017
%t Join[{0, 1, 3}, LinearRecurrence[{1, 1, 1}, {4, 7, 13}, 20]] (* _Vincenzo Librandi_, Mar 28 2017 *)
%o (Magma) I:=[0,1,3,4,7,13]; [n le 6 select I[n] else Self(n-1)+Self(n-2)+Self(n-3): n in [1..40]]; // _Vincenzo Librandi_, Mar 28 2017
%Y Cf. A000073.
%K nonn,easy
%O 0,3
%A _N. J. A. Sloane_, Mar 02 2017
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