%I #9 Feb 02 2021 19:35:29
%S 1,1,1,4,20,158,1539,16970,199879,2460350,31266165,407461893,
%T 5420228329,73352481577,1007312969202,14008437540003,196963172193733,
%U 2796235114720116,40038505601111596,577693117173844307,8392528734991449808,122680472402091278920,1803416089912665770579
%N Number of unlabeled heptagonal 2-trees with n heptagons.
%H Andrew Howroyd, <a href="/A094651/b094651.txt">Table of n, a(n) for n = 0..200</a>
%H G. Labelle, C. Lamathe and P. Leroux, <a href="http://arXiv.org/abs/math.CO/0312424">Labeled and unlabeled enumeration of k-gonal 2-trees</a>, arXiv:math/0312424 [math.CO], Dec 23 2003.
%Y Column k=7 of A340811.
%Y Cf. A054581.
%K nonn
%O 0,4
%A _Vladeta Jovovic_, Jun 06 2004
%E Terms a(20) and beyond from _Andrew Howroyd_, Feb 02 2021