A244460 Number of unlabeled rooted trees with n nodes such that the minimal outdegree of inner nodes equals 6.

1, 0, 0, 0, 0, 0, 1, 2, 2, 2, 2, 2, 4, 7, 12, 16, 21, 25, 34, 47, 70, 103, 147, 201, 276, 377, 527, 743, 1057, 1486, 2088, 2911, 4073, 5704, 8027, 11290, 15897, 22340, 31411, 44159, 62165, 87516, 123296, 173642, 244636, 344684, 485976, 685362, 966971, 1364301

Offset: 7

Author

Joerg Arndt and Alois P. Heinz, Jun 29 2014

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 7..900

Crossrefs

Column k=6 of A244454.

Cf. A244535.

Programs

Maple

b:= proc(n, i, t, k) option remember; `if`(n=0, `if`(t in [0, k],
      1, 0), `if`(i<1 or t>n, 0, add(binomial(b((i-1)$2, k$2)+j-1, j)*
      b(n-i*j, i-1, max(0,t-j), k), j=0..n/i)))
    end:
a:= n-> b(n-1$2, 6$2) -b(n-1$2, 7$2):
seq(a(n), n=7..60);

Mathematica

b[n_, i_, t_, k_] := b[n, i, t, k] = If[n == 0, If[t == 0 || t == k, 1, 0], If[i < 1, 0, Sum[Binomial[b[i - 1, i - 1, k, k] + j - 1, j]*b[n - i*j, i - 1, Max[0, t - j], k], {j, 0, n/i}]] // FullSimplify]; a[n_] := b[n - 1, n - 1, 6, 6] - b[n - 1, n - 1, 7, 7]; Table[a[n], {n, 7, 60}] (* Jean-François Alcover, Feb 06 2015, after Maple *)