A049860 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 0,1,4.

0, 1, 4, 5, 9, 15, 29, 54, 102, 190, 355, 662, 1236, 2307, 4307, 8040, 15009, 28018, 52303, 97637, 182265, 340245, 635156, 1185684, 2213388, 4131865, 7713202, 14398700, 26878923, 50176509, 93667520, 174854817, 326412048, 609333085, 1137478873, 2123400515

Offset

0,3

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

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+2*x^2-3*x^3)/(1-2*x+x^3-x^4). - Harvey P. Dale, Jun 15 2019

Mathematica

LinearRecurrence[{2, 0, -1, 1}, {0, 1, 4, 5}, 50] (* Harvey P. Dale, Jun 15 2019 *)

Crossrefs

Sequence in context: A217685 A251632 A350695 * A010382 A138673 A087948

Adjacent sequences: A049857 A049858 A049859 * A049861 A049862 A049863

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved