A049867 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.

1, 1, 4, 5, 10, 17, 33, 61, 115, 214, 400, 746, 1393, 2600, 4854, 9061, 16915, 31576, 58945, 110036, 205411, 383453, 715815, 1336255, 2494468, 4656574, 8692708, 16227203, 30292300, 56548466, 105562437, 197059777, 367863388

Offset

0,3

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) for n >= 4.

G.f.: (1 - x + 2*x^2 - 2*x^3)/(1 - 2*x + x^3 - x^4). - Stefano Spezia, Dec 26 2021

Crossrefs

Sequence in context: A285289 A022309 A049897 * A054173 A185875 A354080

Adjacent sequences: A049864 A049865 A049866 * A049868 A049869 A049870

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved