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A104581
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Expansion of 1/(1+x+x^3+x^4).
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0
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1, -1, 1, -2, 2, -2, 3, -3, 3, -4, 4, -4, 5, -5, 5, -6, 6, -6, 7, -7, 7, -8, 8, -8, 9, -9, 9, -10, 10, -10, 11, -11, 11, -12, 12, -12, 13, -13, 13, -14, 14, -14, 15, -15, 15, -16, 16, -16, 17, -17, 17, -18, 18, -18, 19, -19, 19, -20, 20, -20, 21, -21, 21, -22, 22, -22, 23, -23, 23, -24, 24, -24, 25, -25, 25, -26, 26, -26
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Diagonal sums of Riordan array (1/(1+x+x^2+x^3+x^4),x/(1+x+x^2+x^3+x^4)). Convolution of (n+1)(-1)^n and A010892.
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (-1,0,-1,-1).
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FORMULA
| a(n)=floor((n+3)/3)(-1)^n; a(n)=sum{k=0..n, (n-k+1)(-1)^(n-k)*2sin(pi*k/3+pi/3)/sqrt(3)}.
G.f.: 1/( (1+x)^2*(1-x+x^2)).
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MATHEMATICA
| CoefficientList[ Series[1/(1 + x + x^3 + x^4), {x, 0, 80}], x] (from Robert G. Wilson v Mar 24 2005)
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CROSSREFS
| Cf. A008620.
Sequence in context: A086161 A002264 A008620 * A113675 A020912 A194990
Adjacent sequences: A104578 A104579 A104580 * A104582 A104583 A104584
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KEYWORD
| easy,sign
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Mar 16 2005
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