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Number of forests with n nodes and height at most 3.
(Formerly M3025 N1225)
4

%I M3025 N1225 #21 May 19 2024 14:03:19

%S 1,3,16,125,1176,12847,160504,2261289,35464816,612419291,11539360944,

%T 235469524237,5170808565976,121535533284999,3043254281853496,

%U 80852247370051793,2270951670959226336,67221368736302224819,2091039845329887687136

%N Number of forests with n nodes and height at most 3.

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H T. D. Noe, <a href="/A000950/b000950.txt">Table of n, a(n) for n = 1..100</a>

%H John Riordan, <a href="https://doi.org/10.1016/S0021-9800(68)80033-X">Forests of labeled trees</a>, J. Combin. Theory, 5 (1968), 90-103.

%F E.g.f.: exp(x*exp(x*exp(x*exp(x)))).

%t nn = 20; Range[0, nn]! CoefficientList[Series[Exp[x*Exp[x*Exp[x*Exp[x]]]], {x, 0, nn}], x] (* _T. D. Noe_, Jun 21 2012 *)

%Y Cf. A000248, A000949-A000951, A052512-A052514.

%Y Column k=3 of A210725. - _Alois P. Heinz_, Mar 15 2013

%K nonn

%O 1,2

%A _N. J. A. Sloane_

%E More terms from _Vladeta Jovovic_, Apr 07 2001