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A163495
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a(0)=0, a(1)=1, a(2)=2. For n >= 3, a(n) = a(n-1) - min(a(n-2), a(n-3)).
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1
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0, 1, 2, 2, 1, -1, -2, -1, 1, 3, 4, 3, 0, -3, -3, 0, 3, 6, 6, 3, -3, -6, -3, 3, 9, 12, 9, 0, -9, -9, 0, 9, 18, 18, 9, -9, -18, -9, 9, 27, 36, 27, 0, -27, -27, 0, 27, 54, 54, 27, -27, -54, -27, 27, 81, 108, 81, 0, -81, -81, 0, 81, 162, 162, 81, -81, -162, -81, 81, 243, 324, 243, 0
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OFFSET
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0,3
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COMMENTS
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a(n+15) = 3*a(n) for all n. - Dion Gijswijt (gijswijt(AT)science.uva.nl) Jul 29 2009 on SeqFan mailing list.
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3).
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FORMULA
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G.f. x*(1 +2*x +2*x^2 +x^3 -x^4 -2*x^5 -x^6 +x^7 +3*x^8 +4*x^9 +3*x^10 -3*x^12 -3*x^13) / (1 - 3*x^15 ). - R. J. Mathar, Jun 22 2011
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MAPLE
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a[0] := 0: a[1] := 1: a[2] := 2: for n from 3 to 80 do a[n] := a[n-1]-min(a[n-2], a[n-3]) end do: seq(a[n], n = 0 .. 80); # Emeric Deutsch, Aug 01 2009
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MATHEMATICA
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CoefficientList[Series[x*(1 +2*x +2*x^2 +x^3 -x^4 -2*x^5 -x^6 +x^7 +3*x^8 +4*x^9 +3*x^10 -3*x^12 -3*x^13)/(1 - 3*x^15 ), {x, 0, 50}], x] (* G. C. Greubel, Jul 26 2017 *)
nxt[{a_, b_, c_}]:={b, c, c-Min[a, b]}; NestList[nxt, {0, 1, 2}, 80][[All, 1]] (* or *) LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3}, {0, 1, 2, 2, 1, -1, -2, -1, 1, 3, 4, 3, 0, -3, -3}, 80] (* Harvey P. Dale, Apr 07 2018 *)
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PROG
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(PARI) x='x+O('x^50); concat([0], Vec(x*(1 +2*x +2*x^2 +x^3 -x^4 -2*x^5 -x^6 +x^7 +3*x^8 +4*x^9 +3*x^10 -3*x^12 -3*x^13)/(1 - 3*x^15 ))) \\ G. C. Greubel, Jul 26 2017
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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