A049860 - OEIS

A049860

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.

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

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OFFSET

0,3

COMMENTS

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

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); 4 initial terms required.

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

AUTHOR

Clark Kimberling

STATUS

approved