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A266093
Number of B-diagrams G such that the number of vertices of G is |G|=n.
1
1, 4, 36, 372, 4372, 57396, 828020, 12962164, 218098356, 3915198836, 74543140404, 1497946963316, 31640513815604, 700059941981812, 16175777760450868, 389308305885650804, 9736819496150623284, 252548355023773152372
OFFSET
0,2
COMMENTS
For a precise definition see the Bousbaa et al. link.
LINKS
Imad Eddine Bousbaa, Ali Chouria, Jean-Gabriel Luque, A combinatorial Hopf algebra for the boson normal ordering problem, arXiv:1512.05937 [math.CO], 2015.
MATHEMATICA
T[0, 0] = 1; T[p_, q_] := T[p, q] = Sum[l! Binomial[j, l] Binomial[q - k + l, l] Binomial[i, j] Binomial[i, k] T[p - i, q - k + l], {i, 1, p}, {j, 0, i}, {k, 0, i}, {l, 0, j}]; a[n_] := Sum[T[n, q], {q, 0, n}]; Table[ a[n], {n, 0, 20}] (* Jean-François Alcover, Dec 21 2015 *)
CROSSREFS
Cf. A265199.
Sequence in context: A371772 A138736 A372461 * A198638 A358954 A019999
KEYWORD
nonn
AUTHOR
Michel Marcus, Dec 21 2015
STATUS
approved