| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 35 |
| 6 | 116 |
| 7 | 392 |
| 8 | 1390 |
| 9 | 4998 |
| 10 | 18321 |
| 11 | 67791 |
| 12 | 253288 |
| 13 | 952527 |
| 14 | 3603761 |
| 15 | 13699516 |
| 16 | 52301427 |
| 17 | 200406183 |
| 18 | 770429000 |
| 19 | 2970400815 |
| 20 | 11482461055 |
| 21 | 44491876993 |
| 22 | 172766558719 |
| 23 | 672186631950 |
| 24 | 2619995431640 |
| 25 | 10228902801505 |
| 26 | 39996342220199 |
| 27 | 156612023001490 |
| 28 | 614044351536722 |
[1,2,4,12,35,116,392,1390,4998,18321,67791,253288, 952527,3603761,13699516,52301427,200406183, 770429000,2970400815,11482461055,44491876993, 172766558719,672186631950,2619995431640, 10228902801505,39996342220199,156612023001490, 614044351536722] |