A060337 - OEIS

%I #10 Mar 23 2022 14:45:32

%S 15,198,1610,10575,61845,336924,1751076,8801325,43141175,207347778,

%T 980828238,4578689115,21135851625,96628899960,438068838536,

%U 1971349880985,8813183238315,39169902510270,173172640973010

%N Number of labeled acyclic digraphs with n nodes containing exactly n-2 points of in-degree zero.

%D F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 19, (1.6.4).

%D R. W. Robinson, Counting labeled acyclic digraphs, pp. 239-273 of F. Harary, editor, New Directions in the Theory of Graphs. Academic Press, NY, 1973.

%H Andrew Howroyd, <a href="/A060337/b060337.txt">Table of n, a(n) for n = 3..500</a>

%H <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (21,-189,955,-2982,5964,-7640,6048,-2688,512).

%F G.f.: x^3*(15 - 117*x + 287*x^2 - 138*x^3 - 300*x^4 + 280*x^5)/((1 - x)*(1 - 2*x)*(1 - 4*x))^3. - _Andrew Howroyd_, Dec 27 2021

%t LinearRecurrence[{21,-189,955,-2982,5964,-7640,6048,-2688,512},{15,198,1610,10575,61845,336924,1751076,8801325,43141175},20] (* _Harvey P. Dale_, Mar 23 2022 *)

%o (PARI) \\ requires A058876.

%o my(T=A058876(25)); vector(#T-2, n, T[n+2][n]) \\ _Andrew Howroyd_, Dec 27 2021

%Y Third column of A058876.

%Y Cf. A003025, A003026.

%K nonn,easy

%O 3,1

%A _Vladeta Jovovic_, Apr 10 2001