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A026530
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a(n) = T(n, floor(n/2)), T given by A026519.
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42
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1, 1, 1, 2, 5, 8, 16, 28, 65, 111, 251, 436, 1016, 1763, 4117, 7176, 16913, 29521, 69865, 122182, 290455, 508595, 1212905, 2126312, 5085224, 8923136, 21389824, 37563930, 90226449, 158563368, 381519416, 670893296, 1616684241, 2844444761
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history;
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internal format)
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OFFSET
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0,4
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LINKS
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FORMULA
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MATHEMATICA
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T[n_, k_]:= T[n, k]= If[k<0 || k>2*n, 0, If[k==0 || k==2*n, 1, If[k==1 || k==2*n-1, Floor[(n+1)/2], If[EvenQ[n], T[n-1, k-2] + T[n-1, k], T[n-1, k-1] + T[n-1, k-2] + T[n-1, k] ]]]]; (* T = A026519 *)
a[n_] := a[n] = Block[{$RecursionLimit = Infinity}, T[n, Floor[n/2]] ];
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PROG
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(Sage)
@CachedFunction
if (k<0 or k>2*n): return 0
elif (k==0 or k==2*n): return 1
elif (k==1 or k==2*n-1): return (n+1)//2
elif (n%2==0): return T(n-1, k) + T(n-1, k-2)
else: return T(n-1, k) + T(n-1, k-1) + T(n-1, k-2)
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CROSSREFS
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Cf. A026519, A026520, A026521, A026522, A026523, A026524, A026525, A026526, A026527, A026528, A026529, A026531, A026532, A026533, A026534, A027262, A027263, A027264, A027265, A027266.
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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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