The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 45 |
| 5 | 174 |
| 6 | 710 |
| 7 | 2829 |
| 8 | 11685 |
| 9 | 49826 |
| 10 | 212370 |
| 11 | 908756 |
| 12 | 3967406 |
| 13 | 17428452 |
| 14 | 76575883 |
| 15 | 339309966 |
| 16 | 1515297265 |
| 17 | 6775762236 |
| 18 | 30392803463 |
| 19 | 137107357008 |
| 20 | 620274107946 |
| 21 | 2810115185408 |
| 22 | 12773447145043 |
| 23 | 58242082395214 |
| 24 | 265937635904625 |
| 25 | 1216485786889994 |
| 26 | 5578551230005231 |
| 27 | 25624367940626478 |
[1,1,4,13,45,174,710,2829,11685,49826,212370, 908756,3967406,17428452,76575883,339309966, 1515297265,6775762236,30392803463,137107357008, 620274107946,2810115185408,12773447145043, 58242082395214,265937635904625,1216485786889994, 5578551230005231,25624367940626478] |