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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.
1
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
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
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
KEYWORD
nonn
STATUS
approved