A244400 Number of unlabeled rooted trees with n nodes and maximal outdegree (branching factor) 4.
1, 2, 6, 17, 49, 136, 386, 1081, 3044, 8549, 24052, 67642, 190426, 536205, 1510920, 4259418, 12014682, 33907056, 95740913, 270468869, 764450150, 2161638413, 6115252839, 17307553766, 49005101669, 138811296158, 393351362321, 1115072623713, 3162183392471
Offset: 5
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 5..1000
Programs
-
Maple
b:= proc(n, i, t, k) option remember; `if`(n=0, 1, `if`(i<1, 0, add(binomial(b((i-1)$2, k$2)+j-1, j)* b(n-i*j, i-1, t-j, k), j=0..min(t, n/i)))) end: a:= n-> b(n-1$2, 4$2) -`if`(k=0, 0, b(n-1$2, 3$2)): seq(a(n), n=5..40);
-
Mathematica
b[n_, i_, t_, k_] := b[n, i, t, k] = If[n == 0, 1, If[i < 1, 0, Sum[Binomial[b[i - 1, i - 1, k, k] + j - 1, j]* b[n - i*j, i - 1, t - j, k], {j, 0, Min[t, n/i]}]] // FullSimplify]; a[n_] := b[n-1, n-1, 4, 4] - If[n == 0, 0, b[n-1, n-1, 3, 3]]; Table[a[n], {n, 5, 40}] (* Jean-François Alcover, Feb 09 2015, after Maple *)