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%I M3026 N1226 #18 Apr 01 2017 00:09:31
%S 1,3,16,125,1296,16087,229384,3687609,66025360,1303751051,28151798544,
%T 659841763957,16681231615816,452357366282655,13095632549137576,
%U 403040561722348913,13138626717852194976,452179922268565180819,16381932383826669204640
%N Number of forests with n nodes and height at most 4.
%D J. Riordan, Forests of labeled trees, J. Combin. Theory, 5 (1968), 90-103.
%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="/A000951/b000951.txt">Table of n, a(n) for n = 1..100</a>
%F E.g.f.: exp(x*exp(x*exp(x*exp(x*exp(x))))).
%t nn = 20; Range[0, nn]! CoefficientList[Series[Exp[x*Exp[x*Exp[x*Exp[x*Exp[x]]]]], {x, 0, nn}], x] (* _T. D. Noe_, Jun 21 2012 *)
%Y Cf. A000248, A000949, A000950, A052512-A052514.
%Y Column k=4 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
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