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 A128504 Row sums of array A128503 (second convolution of Chebyshev's S(n,x)=U(n,x/2) polynomials). 4
 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; text; internal format)
 OFFSET 0,2 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). [John M. Campbell, Jul 10 2011] LINKS FORMULA a(n)=sum( A128503(n,m),m=0..floor(n/2)), n>=0. G.f.: 1/(1-x+x^2)^3. a(n) = (floor(n/3)+1)*(floor(n/3)-floor((n-1)/3)+(3/2)*(floor(n/3)+2)*(3*floor((n+1)/3)-n))*(-1)^n. - Tani Akinari, Jul 03 2013 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}] (* John M. Campbell, Jul 10 2011 *) PROG (PARI) Vec(1/(1-x+x^2)^3+O(x^66)) \\ Joerg Arndt, Jul 02 2013 CROSSREFS Sequence in context: A214101 A286952 A100052 * A193822 A202699 A058137 Adjacent sequences:  A128501 A128502 A128503 * A128505 A128506 A128507 KEYWORD sign,easy AUTHOR Wolfdieter Lang Apr 04 2007 STATUS approved

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Last modified May 17 12:55 EDT 2021. Contains 343971 sequences. (Running on oeis4.)