login
A350772
Triangle read by rows: T(n,k) is the number of n-element unlabeled series-parallel posets with k connected components.
0
1, 1, 1, 3, 1, 1, 9, 4, 1, 1, 30, 12, 4, 1, 1, 103, 45, 13, 4, 1, 1, 375, 160, 48, 13, 4, 1, 1, 1400, 613, 175, 49, 13, 4, 1, 1, 5380, 2354, 680, 178, 49, 13, 4, 1, 1
OFFSET
1,4
EXAMPLE
Triangle begins:
1;
1, 1;
3, 1, 1;
9, 4, 1, 1;
30, 12, 4, 1, 1;
103, 45, 13, 4, 1, 1;
375, 160, 48, 13, 4, 1, 1;
1400, 613, 175, 49, 13, 4, 1, 1;
5380, 2354, 680, 178, 49, 13, 4, 1, 1;
...
CROSSREFS
Row sums give A003430.
Column 1 is A007453.
Cf. A263864 (all posets), A349488 (disconnected).
Sequence in context: A100537 A069605 A080510 * A350783 A124496 A074881
KEYWORD
nonn,tabl
AUTHOR
STATUS
approved