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A049870 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, 2, 4, 6, 11, 20, 38, 71, 133, 248, 463, 864, 1613, 3011, 5621, 10493, 19588, 36566, 68260, 127425, 237872, 444050, 828935, 1547423, 2888668, 5392451, 10066414, 18791583, 35079383, 65484803, 122244437, 228201074, 425996728 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

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); 4 initial terms required.

MATHEMATICA

LinearRecurrence[{2, 0, -1, 1}, {1, 2, 4, 6}, 40] (* Harvey P. Dale, Mar 23 2015 *)

CROSSREFS

Sequence in context: A199926 A068330 A017993 * A093970 A333098 A107428

Adjacent sequences:  A049867 A049868 A049869 * A049871 A049872 A049873

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)