A049873 a(n) = Sum{a(k): k=0,1,2,...,n-4,n-2,n-1}; a(n-3) is not a summand; initial terms are 2,2,3.

2, 2, 3, 5, 10, 19, 36, 67, 125, 233, 435, 812, 1516, 2830, 5283, 9862, 18410, 34367, 64155, 119762, 223567, 417346, 779085, 1454365, 2714951, 5068163, 9461046, 17661506, 32969800, 61546717, 114892974, 214477654, 400378391, 747410525, 1395236370, 2604572003

Offset

0,1

Links

Table of n, a(n) for n=0..35.

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).

G.f.: (-x^3+x^2+2*x-2)/(x^4-x^3+2*x-1).

Mathematica

LinearRecurrence[{2, 0, -1, 1}, {2, 2, 3, 5}, 40] (* Harvey P. Dale, May 08 2017 *)

Crossrefs

Sequence in context: A344708 A322113 A153900 * A127180 A317809 A249241

Adjacent sequences: A049870 A049871 A049872 * A049874 A049875 A049876

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved