OFFSET
0,3
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Julien Leroy, Michel Rigo, Manon Stipulanti, Counting the number of non-zero coefficients in rows of generalized Pascal triangles Discrete Mathematics 340 (2017), 862-881. See Example 43.
Index entries for linear recurrences with constant coefficients, signature (1,1,1).
FORMULA
a(n) = A000073(n+2), n >= 3. - R. J. Mathar, Mar 03 2017
G.f.: x*(1 + 2*x - x^3 - x^4)/(1 - x - x^2 - x^3). - Bruno Berselli, Mar 03 2017
MATHEMATICA
Join[{0, 1, 3}, LinearRecurrence[{1, 1, 1}, {4, 7, 13}, 20]] (* Vincenzo Librandi, Mar 28 2017 *)
PROG
(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
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Mar 02 2017
STATUS
approved