OFFSET
1,6
COMMENTS
Equivalently, the number of rooted connected graphs on n unlabeled nodes with k blocks where every block is a complete graph.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1275
EXAMPLE
Triangle begins:
1;
0, 1;
0, 1, 2;
0, 1, 3, 4;
0, 1, 5, 10, 9;
0, 1, 6, 20, 30, 20;
0, 1, 8, 33, 77, 91, 48;
0, 1, 9, 49, 152, 277, 268, 115;
0, 1, 11, 68, 269, 655, 969, 790, 286;
...
PROG
(PARI)
EulerMT(u)={my(n=#u, p=x*Ser(u), vars=variables(p)); Vec(exp( sum(i=1, n, substvec(p + O(x*x^(n\i)), vars, apply(v->v^i, vars))/i ))-1)}
R(n)={my(v=[1]); for(i=2, n, v=concat([1], EulerMT(y*EulerMT(v)))); [Vecrev(p) | p <- v]}
{ my(T=R(10)); for(n=1, #T, print(T[n])) }
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Andrew Howroyd, Aug 29 2018
STATUS
approved