The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 16 |
| 3 | 54 |
| 4 | 177 |
| 5 | 596 |
| 6 | 2024 |
| 7 | 6869 |
| 8 | 23285 |
| 9 | 78942 |
| 10 | 267681 |
| 11 | 907708 |
| 12 | 3078001 |
| 13 | 10437337 |
| 14 | 35392507 |
| 15 | 120014445 |
| 16 | 406963770 |
| 17 | 1379996360 |
| 18 | 4679507294 |
| 19 | 15868004855 |
| 20 | 53807711762 |
| 21 | 182459601684 |
| 22 | 618712543947 |
| 23 | 2098027226581 |
| 24 | 7114318736716 |
[4,16,54,177,596,2024,6869,23285,78942,267681, 907708,3078001,10437337,35392507,120014445, 406963770,1379996360,4679507294,15868004855, 53807711762,182459601684,618712543947, 2098027226581,7114318736716] |