The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 38 |
| 5 | 111 |
| 6 | 477 |
| 7 | 1593 |
| 8 | 6954 |
| 9 | 25101 |
| 10 | 111245 |
| 11 | 421669 |
| 12 | 1895942 |
| 13 | 7424769 |
| 14 | 33816664 |
| 15 | 135567201 |
| 16 | 624118470 |
| 17 | 2547578027 |
| 18 | 11830222149 |
| 19 | 48999526377 |
| 20 | 229130337164 |
| 21 | 960584070247 |
| 22 | 4517804622196 |
| 23 | 19133276961661 |
| 24 | 90428499614550 |
| 25 | 386287368914329 |
| 26 | 1833395676854963 |
| 27 | 7890147722387035 |
| 28 | 37584984231943110 |
[1,1,4,9,38,111,477,1593,6954,25101,111245,421669, 1895942,7424769,33816664,135567201,624118470, 2547578027,11830222149,48999526377,229130337164, 960584070247,4517804622196,19133276961661, 90428499614550,386287368914329,1833395676854963, 7890147722387035,37584984231943110] |