The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 24 |
| 4 | 108 |
| 5 | 406 |
| 6 | 1572 |
| 7 | 5961 |
| 8 | 22788 |
| 9 | 87209 |
| 10 | 335010 |
| 11 | 1290376 |
| 12 | 4983162 |
| 13 | 19286891 |
| 14 | 74797176 |
| 15 | 290586771 |
| 16 | 1130716508 |
| 17 | 4406049037 |
| 18 | 17191077082 |
| 19 | 67152699384 |
| 20 | 262594530318 |
| 21 | 1027851765350 |
| 22 | 4026831276662 |
| 23 | 15788979175102 |
| 24 | 61954847930374 |
| 25 | 243278117470476 |
| 26 | 955907159445522 |
[1,6,24,108,406,1572,5961,22788,87209,335010, 1290376,4983162,19286891,74797176,290586771, 1130716508,4406049037,17191077082,67152699384, 262594530318,1027851765350,4026831276662, 15788979175102,61954847930374,243278117470476, 955907159445522] |