| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 83 |
| 6 | 356 |
| 7 | 1599 |
| 8 | 7434 |
| 9 | 35381 |
| 10 | 171508 |
| 11 | 843419 |
| 12 | 4197179 |
| 13 | 21094355 |
| 14 | 106915928 |
| 15 | 545859112 |
| 16 | 2804656069 |
| 17 | 14491370996 |
| 18 | 75248398034 |
| 19 | 392476363133 |
| 20 | 2055245992376 |
| 21 | 10801442696736 |
| 22 | 56953957110855 |
| 23 | 301207378815752 |
[1,2,6,21,83,356,1599,7434,35381,171508,843419, 4197179,21094355,106915928,545859112,2804656069, 14491370996,75248398034,392476363133, 2055245992376,10801442696736,56953957110855, 301207378815752] |