|
|
A339650
|
|
Triangle read by rows: T(n,k) is the number of trees with n leaves of exactly k colors and all non-leaf nodes having degree 3.
|
|
7
|
|
|
1, 0, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 4, 6, 3, 0, 1, 10, 30, 36, 15, 0, 2, 27, 140, 310, 300, 105, 0, 2, 74, 663, 2376, 3990, 3150, 945, 0, 4, 226, 3186, 17304, 44850, 59805, 39690, 10395, 0, 6, 710, 15642, 123508, 462735, 925890, 1018710, 582120, 135135
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,9
|
|
COMMENTS
|
See table 4.2 in the Johnson reference.
|
|
LINKS
|
|
|
FORMULA
|
T(n,k) = Sum_{i=0..k} (-1)^(k-i)*binomial(k,i)*A339649(n,i).
|
|
EXAMPLE
|
Triangle begins:
1;
0, 1;
0, 1, 1;
0, 1, 2, 1;
0, 1, 4, 6, 3;
0, 1, 10, 30, 36, 15;
0, 2, 27, 140, 310, 300, 105;
0, 2, 74, 663, 2376, 3990, 3150, 945;
0, 4, 226, 3186, 17304, 44850, 59805, 39690, 10395;
...
|
|
PROG
|
(PARI) \\ here U(n, k) is column k of A339649 as a vector.
R(n, k)={my(v=vector(n)); v[1]=k; for(n=2, n, v[n]=sum(j=1, (n-1)\2, v[j]*v[n-j]) + if(n%2, 0, binomial(v[n/2]+1, 2))); v}
U(n, k)={my(g=x*Ser(R(n, k))); Vec(1 + g + (subst(g + O(x*x^(n\3)), x, x^3) - g^3)/3)}
M(n, m=n)={my(v=vector(m+1, k, U(n, k-1)~)); Mat(vector(m+1, k, k--; sum(i=0, k, (-1)^(k-i)*binomial(k, i)*v[1+i])))}
{my(T=M(10)); for(n=1, #T~, print(T[n, ][1..n]))}
|
|
CROSSREFS
|
Main diagonal is A001147(n-2) for n >= 2.
|
|
KEYWORD
|
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|