A049855 a(n) = Sum{a(k): k=0,1,2,...,n-3,n-1}; a(n-2) is not a summand; 2 initial terms required.

2, 3, 3, 5, 10, 18, 31, 54, 95, 167, 293, 514, 902, 1583, 2778, 4875, 8555, 15013, 26346, 46234, 81135, 142382, 249863, 438479, 769477, 1350338, 2369678, 4158495, 7297650, 12806483, 22473811, 39438789, 69210250, 121455522, 213139583, 374033894, 656383727, 1151873143

Offset

0,1

Links

Table of n, a(n) for n=0..37.

Index entries for linear recurrences with constant coefficients, signature (2,-1,1).

Formula

a(n) = 2*a(n-1) - a(n-2) + a(n-3); 3 initial terms required.

G.f.: (2 - x - x^2)/(1 - 2*x + x^2 - x^3). - Stefano Spezia, Sep 10 2022

Mathematica

LinearRecurrence[{2, -1, 1}, {2, 3, 3}, 38] (* Stefano Spezia, Sep 10 2022 *)

Crossrefs

Cf. A049856.

Sequence in context: A019460 A329057 A236165 * A286868 A326184 A326053

Adjacent sequences: A049852 A049853 A049854 * A049856 A049857 A049858

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved