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A047081 a(n) = Sum_{k=0..n} T(n, k), array T as in A047080. 9
1, 2, 3, 6, 11, 20, 37, 68, 125, 230, 423, 778, 1431, 2632, 4841, 8904, 16377, 30122, 55403, 101902, 187427, 344732, 634061, 1166220, 2145013, 3945294, 7256527, 13346834, 24548655, 45152016, 83047505, 152748176, 280947697, 516743378, 950439251, 1748130326, 3215312955, 5913882532, 10877325813 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
From G. C. Greubel, Oct 31 2022: (Start)
G.f.: (1 + x)/(1 - x - x^2 - x^3).
a(n) = A000073(n+1) + A000073(n+2). (End)
MATHEMATICA
LinearRecurrence[{1, 1, 1}, {1, 2, 3}, 61] (* G. C. Greubel, Oct 31 2022 *)
PROG
(Magma) [n le 3 select n else Self(n-1) +Self(n-2) +Self(n-3): n in [1..60]]; // G. C. Greubel, Oct 31 2022
(SageMath)
@CachedFunction
def a(n): return (n+1) if (n<3) else a(n-1) +a(n-2) +a(n-3) # a = A047081
[a(n) for n in (0..60)] # G. C. Greubel, Oct 31 2022
CROSSREFS
Sequence in context: A355560 A001590 A078042 * A115792 A054177 A186546
KEYWORD
easy,nonn
AUTHOR
EXTENSIONS
Data corrected by G. C. Greubel, Oct 31 2022
STATUS
approved

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Last modified March 29 08:59 EDT 2024. Contains 371268 sequences. (Running on oeis4.)