A049875 a(n) = Sum{a(k): k=0,1,2,...,n-4,n-2,n-1}; a(n-3) is not a summand; 3 initial terms required.

2, 3, 3, 6, 11, 22, 41, 77, 143, 267, 498, 930, 1736, 3241, 6050, 11294, 21083, 39357, 73470, 137151, 256028, 477943, 892205, 1665533, 3109151, 5804040, 10834752, 20225886, 37756883, 70483054, 131574974, 245618951, 458511731

Offset

0,1

Links

Table of n, a(n) for n=0..32.

Index entries for linear recurrences with constant coefficients, signature (2,0,-1,1).

Formula

a(n) = 2*a(n-1)-a(n-3)+a(n-4); 4 initial terms required.

G.f.: (x - 1)*(-2*x^2 + x + 2)/(x^4 - x^3 + 2*x - 1). - Chai Wah Wu, Feb 20 2023

Mathematica

LinearRecurrence[{2, 0, -1, 1}, {2, 3, 3, 6}, 40] (* Harvey P. Dale, Nov 21 2023 *)

Crossrefs

Sequence in context: A059191 A124063 A054630 * A180887 A329748 A173094

Adjacent sequences: A049872 A049873 A049874 * A049876 A049877 A049878

Keyword

nonn

Author

Clark Kimberling

Status

approved