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Consider the family of multigraphs enriched by the species of arborescences. Sequence gives number of those multigraphs with n labeled edges.
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%I #12 Jan 12 2021 20:54:01

%S 1,1,4,30,338,5169,101251,2446806,71043973,2429762734,96364601877,

%T 4375603494478,225044659552381,12990629618136191,834981228656630494,

%U 59346659738963806022,4635924974380060251228,395864230878802130389079,36773114396103232927777067

%N Consider the family of multigraphs enriched by the species of arborescences. Sequence gives number of those multigraphs with n labeled edges.

%D G. Paquin, Dénombrement de multigraphes enrichis, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004.

%H Andrew Howroyd, <a href="/A099712/b099712.txt">Table of n, a(n) for n = 0..100</a>

%H G. Paquin, <a href="/A038205/a038205.pdf">Dénombrement de multigraphes enrichis</a>, Mémoire, Math. Dept., Univ. Québec à Montréal, 2004. [Cached copy, with permission]

%F E.g.f.: B(R(x)) where B(x) is the e.g.f. of A014500 and R(x) is the e.g.f. of A000169. - _Andrew Howroyd_, Jan 12 2021

%o (PARI) \\ R(n) is A000169 as e.g.f.; EnrichedGnSeq defined in A098620.

%o R(n)={-lambertw(-x + O(x*x^n))}

%o EnrichedGnSeq(R(20)) \\ _Andrew Howroyd_, Jan 12 2021

%Y Cf. A000169, A014500, A098620, A099713, A099714, A099715.

%K nonn

%O 0,3

%A _N. J. A. Sloane_, Oct 26 2004

%E Terms a(12) and beyond from _Andrew Howroyd_, Jan 12 2021