A049876 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 2,3,4.

2, 3, 4, 7, 13, 25, 47, 88, 164, 306, 571, 1066, 1990, 3715, 6935, 12946, 24167, 45114, 84217, 157213, 293479, 547855, 1022714, 1909162, 3563948, 6653037, 12419626, 23184466, 43279843, 80793097, 150821354, 281547331, 525581408, 981134559, 1831543141, 3419052205

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

Mathematica

LinearRecurrence[{2 , 0, -1, 1}, {2, 3, 4, 7}, 40] (* Harvey P. Dale, May 02 2012 *)

Crossrefs

Sequence in context: A099779 A270440 A000690 * A049795 A329111 A014251

Adjacent sequences: A049873 A049874 A049875 * A049877 A049878 A049879

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved