The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 37 |
| 5 | 146 |
| 6 | 532 |
| 7 | 1939 |
| 8 | 7867 |
| 9 | 30759 |
| 10 | 119428 |
| 11 | 494439 |
| 12 | 1998117 |
| 13 | 8031890 |
| 14 | 33663606 |
| 15 | 138767875 |
| 16 | 569739552 |
| 17 | 2408265131 |
| 18 | 10058849444 |
| 19 | 41885466587 |
| 20 | 178161102199 |
| 21 | 751113795845 |
| 22 | 3159201427573 |
| 23 | 13502875061936 |
| 24 | 57323664729986 |
| 25 | 242912678538629 |
| 26 | 1042256626250547 |
| 27 | 4448498168340005 |
[1,1,4,12,37,146,532,1939,7867,30759,119428, 494439,1998117,8031890,33663606,138767875, 569739552,2408265131,10058849444,41885466587, 178161102199,751113795845,3159201427573, 13502875061936,57323664729986,242912678538629, 1042256626250547,4448498168340005] |