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A084614
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Triangle, read by rows, where the n-th row lists the (2*n+1) coefficients of (1 + x - 3*x^2)^n.
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4
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1, 1, 1, -3, 1, 2, -5, -6, 9, 1, 3, -6, -17, 18, 27, -27, 1, 4, -6, -32, 19, 96, -54, -108, 81, 1, 5, -5, -50, 5, 211, -15, -450, 135, 405, -243, 1, 6, -3, -70, -30, 366, 181, -1098, -270, 1890, -243, -1458, 729, 1, 7, 0, -91, -91, 546, 637, -2015, -1911, 4914, 2457, -7371, 0, 5103, -2187, 1, 8, 4, -112, -182, 728, 1456
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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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T(n, k) = Sum_{j=0..k} binomial(n, k-j)*binomial(k-j, j)*(-3)^j, for 0 <= k <= 2*n.
T(n, 2*n) = (-3)^n.
T(n, 2*n-1) = (-1)^(n-1)*A027471(n+1), n >= 1.
Sum_{k=0..2*n} T(n, k) = (-1)^n.
Sum_{k=0..2*n} (-1)^k*T(n, k) = (-3)^n. (End)
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EXAMPLE
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Rows:
1;
1, 1, -3;
1, 2, -5, -6, 9;
1, 3, -6, -17, 18, 27, -27;
1, 4, -6, -32, 19, 96, -54, -108, 81;
1, 5, -5, -50, 5, 211, -15, -450, 135, 405, -243;
1, 6, -3, -70, -30, 366, 181, -1098, -270, 1890, -243, -1458, 729;
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MATHEMATICA
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With[{eq= (1+x-3*x^2)}, Flatten[Table[CoefficientList[Expand[eq^n], x], {n, 0, 13}]]] (* G. C. Greubel, Mar 02 2017 *)
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PROG
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(PARI) for(n=0, 12, for(k=0, 2*n, t=polcoeff((1+x-3*x^2)^n, k, x); print1(t", ")); print(" "))
(Magma)
A084614:= func< n, k | (&+[Binomial(n, k-j)*Binomial(k-j, j)*(-3)^j: j in [0..k]]) >;
(SageMath)
def A084614(n, k): return ( (1+x-3*x^2)^n ).series(x, 30).list()[k]
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CROSSREFS
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KEYWORD
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sign,tabf
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AUTHOR
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STATUS
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approved
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