The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 8 |
| 3 | 20 |
| 4 | 57 |
| 5 | 166 |
| 6 | 538 |
| 7 | 1762 |
| 8 | 6045 |
| 9 | 21040 |
| 10 | 74628 |
| 11 | 267598 |
| 12 | 970134 |
| 13 | 3544416 |
| 14 | 13043650 |
| 15 | 48283236 |
| 16 | 179665425 |
| 17 | 671564330 |
| 18 | 2520312810 |
| 19 | 9492124534 |
| 20 | 35863942748 |
| 21 | 135893383596 |
| 22 | 516258841134 |
| 23 | 1965906973886 |
| 24 | 7502329984510 |
| 25 | 28687263026656 |
| 26 | 109893836400756 |
| 27 | 421684916479018 |
[1,3,8,20,57,166,538,1762,6045,21040,74628,267598, 970134,3544416,13043650,48283236,179665425, 671564330,2520312810,9492124534,35863942748, 135893383596,516258841134,1965906973886, 7502329984510,28687263026656,109893836400756, 421684916479018] |