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A271386 Discriminants of the polynomials T_n(x) = Product_{k=0..n} (x - k(k + 1)/2). 1

%I

%S 1,1,36,291600,1851776640000,23813032808678400000000,

%T 1333916640950593574375424000000000000,

%U 618764594221522786972353235328676003840000000000000000

%N Discriminants of the polynomials T_n(x) = Product_{k=0..n} (x - k(k + 1)/2).

%C Discriminants of the polynomials T_n(x) = -((-1)^n*2^(-n-1)*cos(Pi*sqrt(8 x+1)/2)*Gamma(n-sqrt(8 x+1)/2+3/2)*Gamma(n+sqrt(8 x+1)/2+3/2))/Pi, where Gamma(x) is the gamma function.

%C T_n (x) is described as a polynomial of degree (n + 1) with leading coefficient 1, and with first (n+1) triangular numbers as roots.

%C T_n(x) have generating function G(x,t) = x + (x^2 - x)*t + (x^3 - 4*x^2 + 3*x)*t^2 + (x^4 - 10*x^3 + 27*x^2 - 18*x)*t^3 + …

%C The next term is too large to include.

%H Ilya Gutkovskiy, <a href="/A271386/b271386.txt">Table of n, a(n) for n = 0..25</a>

%H Ilya Gutkovskiy, <a href="/A271386/a271386.pdf">Polynomials T_n(x)</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TriangularNumber.html">Triangular Number</a>

%e The first few polynomials are:

%e T_0(x) = x;

%e T_1(x) = x^2 - x;

%e T_2(x) = x^3 - 4*x^2 + 3*x;

%e T_3(x) = x^4 - 10*x^3 + 27*x^2 - 18*x;

%e T_4(x) = x^5 - 20*x^4 + 127*x^3 - 288*x^2 + 180*x;.

%e T_5(x) = x^6 - 35*x^5 + 427*x^4 - 2193*x^3 + 4500*x^2 - 2700*x, etc.

%e …

%e a(3) = discriminant T_3(x) = 291600.

%t Table[Discriminant[(-1/2)^n x Pochhammer[3/2 - Sqrt[1 + 8 x]/2, n] Pochhammer[(3 + Sqrt[1 + 8 x])/2, n], x], {n, 0, 7}]

%Y Cf. A000217, A128813.

%K nonn

%O 0,3

%A _Ilya Gutkovskiy_, Apr 06 2016

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Last modified February 20 02:07 EST 2018. Contains 299357 sequences. (Running on oeis4.)