A049866 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 1,1,3.

1, 1, 3, 4, 8, 14, 27, 50, 94, 175, 327, 610, 1139, 2126, 3969, 7409, 13831, 25819, 48198, 89974, 167960, 313541, 585306, 1092626, 2039671, 3807577, 7107834, 13268623, 24769340, 46238423, 86316057, 161131397, 300793711, 561509788, 1048204236, 1956746158, 3652776239

Offset

0,3

Links

Table of n, a(n) for n=0..36.

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

Mathematica

LinearRecurrence[{2, 0, -1, 1}, {1, 1, 3, 4}, 40] (* Harvey P. Dale, Jul 28 2019 *)

Crossrefs

Sequence in context: A136425 A331330 A005907 * A118355 A026632 A332985

Adjacent sequences: A049863 A049864 A049865 * A049867 A049868 A049869

Keyword

nonn,easy,changed

Author

Clark Kimberling

Status

approved