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A027050
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a(n) = T(n,2n-1), T given by A027023.
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2
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1, 3, 5, 11, 25, 59, 145, 367, 949, 2495, 6645, 17883, 48541, 132711, 365073, 1009647, 2805365, 7827167, 21918997, 61584891, 173550677, 490408623, 1389206065, 3944231887, 11221911849, 31989733339, 91354992405, 261322661051
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OFFSET
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1,2
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LINKS
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FORMULA
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Conjecture D-finite with recurrence (-n+1)*a(n) +3*(2*n-3)*a(n-1) +(-7*n+10)*a(n-2) +2*(-4*n+19)*a(n-3) +(5*n-23)*a(n-4) +(2*n-5)*a(n-5) +3*(n-4)*a(n-6)=0. - R. J. Mathar, Jun 24 2020
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MAPLE
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T:= proc(n, k) option remember;
if k<3 or k=2*n then 1
else add(T(n-1, k-j), j=1..3)
fi
end:
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MATHEMATICA
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T[n_, k_]:= T[n, k]= If[n<0, 0, If[k<3 || k==2*n, 1, Sum[T[n-1, k-j], {j, 3}]]]; Table[T[n, 2*n-1], {n, 30}] (* G. C. Greubel, Nov 05 2019 *)
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PROG
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(Sage)
@CachedFunction
def T(n, k):
if (k<3 or k==2*n): return 1
else: return sum(T(n-1, k-j) for j in (1..3))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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