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A128504
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Row sums of array A128503 (second convolution of Chebyshev's S(n,x)=U(n,x/2) polynomials).
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1
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1, 3, 3, -2, -9, -9, 3, 18, 18, -4, -30, -30, 5, 45, 45, -6, -63, -63, 7, 84, 84, -8, -108, -108, 9, 135, 135, -10, -165, -165, 11, 198, 198, -12, -234, -234, 13, 273, 273, -14, -315, -315, 15, 360, 360, -16, -408, -408, 17, 459, 459
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Second convolution of A010892. Convolution of A099254 with A010892.
a(n) equals the coefficient of x^2 of the characteristic polynomial of the (n+2)X(n+2) tridiagonal matrix with 1's along the main diagonal, the superdiagonal, and the subdiagonal (see Mathematica code below). [From John M. Campbell, Jul 10 2011]
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FORMULA
| a(n)=sum( A128503(n,m),m=0..floor(n/2)), n>=0.
G.f.: 1/(1-x+x^2)^3.
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MATHEMATICA
| Table[Coefficient[CharacteristicPolynomial[Array[KroneckerDelta[#1, #2] + KroneckerDelta[#1, #2 - 1] + KroneckerDelta[#1, #2 + 1] &, {n + 2, n + 2}], x], x^2], {n, 0, 70}] (* From John M. Campbell, Jul 10 2011 *)
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CROSSREFS
| Sequence in context: A158468 A200770 A100052 * A193822 A202699 A058137
Adjacent sequences: A128501 A128502 A128503 * A128505 A128506 A128507
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KEYWORD
| sign,easy
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AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Apr 04 2007
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