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A135689
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a(n) = a(n-2) - (a(floor(n/2)) - a(abs(floor(n/2) - 1))) if (n mod 2 = 0), otherwise a(n-1) - (a(abs(floor(n/2) - 2)) - a(abs(floor(n/2) - 3))).
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4
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0, 1, -1, -2, 1, 2, 2, 1, -1, 1, -2, -1, -2, -5, -1, -2, 1, 1, -1, 0, 2, 4, 1, -1, 2, 5, 5, 4, 1, 2, 2, 5, -1, -5, -1, 0, 1, -2, 0, 0, -2, 0, -4, -5, -1, -3, 1, -1, -2, 1, -5, -3, -5, -8, -4, -7, -1, -1, -2, -1, -2, 1, -5, -6, 1, 1, 5, 2, 1, 7, 0, 4, -1, -5, 2, 1, 0, -1, 0, 3, 2, 0, 0, 0, 4, 6, 5, 3, 1, 5, 3, 4, -1, -5, 1, 3, 2, -2, -1, 1, 5
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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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a(n) = a(n-2) - (a(floor(n/2)) - a(abs(floor(n/2) - 1))) if (n mod 2 = 0), otherwise a(n-1) - (a(abs(floor(n/2) - 2)) - a(abs(floor(n/2) - 3))).
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MATHEMATICA
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a[n_]:= a[n] = If[n<2, n, If[n<4, 1-n, If[Mod[n, 2]==0, a[n-2] - (a[Floor[n/2]] - a[Abs[Floor[n/2] -1]]), a[n-1] - (a[Abs[Floor[n/2] -2]] - a[Abs[Floor[n/2] - 3]])] ]]; Table[a[n], {n, 0, 110}]
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PROG
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(Sage)
if (n<4): return [0, 1, -1, -2][n]
elif ((n%2)==0): return a(n-2) - (a((n//2)) - a(abs((n//2) - 1)))
else: return a(n-1) - (a(abs((n//2) - 2)) - a(abs((n//2) - 3)))
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CROSSREFS
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KEYWORD
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sign,easy,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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