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Triangle read by rows: T(n,k) is the unreduced numerator of the k-th weight in the quadrature rule for parabolic runout spline with respect to a mesh of n + 1 points.
3

%I #23 Jan 05 2019 05:20:41

%S 0,1,1,1,4,1,3,9,9,3,13,44,30,44,13,35,115,90,90,115,35,16,53,40,46,

%T 40,53,16,131,433,330,366,366,330,433,131,179,592,450,504,486,504,450,

%U 592,179,163,539,410,458,446,446,458,410,539,163,668,2209,1680,1878,1824,1842,1824,1878,1680,2209,668

%N Triangle read by rows: T(n,k) is the unreduced numerator of the k-th weight in the quadrature rule for parabolic runout spline with respect to a mesh of n + 1 points.

%C The weights in this quadrature rule are T(n,k)/A321122(n), 0 <= k <= n. For n = 1, 2, 3, we obtain the trapezoid rule, Simpson's rule, and Simpson's 3/8 rule, respectively.

%D Harold J. Ahlberg, Edwin N. Nilson and Joseph L. Walsh, The Theory of Splines and Their Applications, Academic Press, 1967. See p. 47, Table 2.5.3.

%H Franck Maminirina Ramaharo, <a href="/A321121/b321121.txt">Rows n = 0..150 of triangle, flattened</a>

%H Harold J. Ahlberg, Edwin N. Nilson and Joseph L. Walsh, <a href="https://doi.org/10.1016/S0076-5392(08)61988-8">Chapter II. The Cubic Spline</a>, Mathematics in Science and Engineering Volume 38 (1967), pp. 9-74.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas">Newton-Cotes formulas</a>

%F T(n,k) = T(n,n-k).

%F T(0,0) = 0 and T(n,k) = A093735(n,k) for n = 1, 2, 3.

%F Let s = -2 + sqrt(3), and define e(n) = s*(2 + s)*(-1 + s^n)/(2*(1 - s)*(-s + s^n)), f(n,k) = 6*s^(1 - k)*(s^(2*k) + s^n)/((1 - s)*(-s + s^n)), and w(n,0) = 1/4 + e(n)/6, w(n,1) = 2 - (1 + 1/6)*e(n), w(n,k) = 1 + f(n,k)/4 for 2 <= k <= n - 2. Then T(n,k) = A321122(n)*w(n,k) for 0 <= k <= n, n >= 3.

%e Triangle begins (denominator is factored out):

%e 0; 1/4

%e 1, 1; 1/2

%e 1, 4, 1; 1/3

%e 3, 9, 9, 3; 1/8

%e 13, 44, 30, 44, 13; 1/36

%e 35, 115, 90, 90, 115, 35; 1/96

%e 16, 53, 40, 46, 40, 53, 16; 1/44

%e 131, 433, 330, 366, 366, 330, 433, 131; 1/360

%e 179, 592, 450, 504, 486, 504, 450, 592, 179; 1/492

%e 163, 539, 410, 458, 446, 446, 458, 410, 539, 163; 1/448

%e ...

%t s = -2 + Sqrt[3];

%t e[n_] := s*(2 + s)*(-1 + s^n)/(2*(1 - s)*(-s + s^n));

%t f[n_, k_] := 6*s^(1 - k)*(s^(2*k) + s^n)/((1 - s)*(-s + s^n));

%t w[n_, k_] := If[k == 0 || k == n, 1/4 + e[n]/6, If[k == 1 || k == n - 1, 2 - (1 + 1/6)*e[n], 1 + f[n, k]/4]];

%t a321122[n_] := LCM @@ Table[Denominator[FullSimplify[w[n, k]]], {k, 0, n}]

%t Join[{0, 1, 1, 1, 4, 1}, Table[FullSimplify[a321122[n]*w[n, k]], {n, 3, 12}, {k, 0, n}]] // Flatten

%o (Maxima)

%o s : -2 + sqrt(3)$

%o e(n) := s*(2 + s)*(-1 + s^n)/(2*(1 - s)*(-s + s^n))$

%o f(n, k) := 6*s^(1 - k)*(s^(2*k) + s^n)/((1 - s)*(-s + s^n))$

%o w(n, k) := if k = 0 or k = n then 1/4 + e(n)/6 else if k = 1 or k = n - 1 then 2 - (1 + 1/6)*e(n) else 1 + f(n, k)/4$

%o a321122(n) := lcm(makelist(denom(fullratsimp(w(n, k))), k, 0, n))$

%o append([0, 1, 1, 1, 4, 1], create_list(fullratsimp(a321122(n)*w(n, k)), n, 3, 12, k, 0, n));

%Y Cf. A321122 (Common denominators).

%Y Cf. A093735/A093736 (Newton-Cotes formulas), A100640/A100641 (Cotesian numbers), A321118/A321119 (Holladay-Sard best quadrature formulas).

%K nonn,easy,tabl,frac

%O 0,5

%A _Franck Maminirina Ramaharo_, Nov 16 2018