The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 1612 |
| 3 | 35440 |
| 4 | 375756 |
| 5 | 2499284 |
| 6 | 12088256 |
| 7 | 46481536 |
| 8 | 150444840 |
| 9 | 425961012 |
| 10 | 1083934148 |
| 11 | 2528257072 |
| 12 | 5485610260 |
| 13 | 11197641780 |
| 14 | 21695822168 |
| 15 | 40183275392 |
| 16 | 71552257168 |
| 17 | 123070684884 |
| 18 | 205276219260 |
| 19 | 333121856624 |
| 20 | 527422812316 |
[20,1612,35440,375756,2499284,12088256,46481536, 150444840,425961012,1083934148,2528257072, 5485610260,11197641780,21695822168,40183275392, 71552257168,123070684884,205276219260, 333121856624,527422812316] |