| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 0 |
| 4 | 3 |
| 5 | 6 |
| 6 | 7 |
| 7 | 20 |
| 8 | 42 |
| 9 | 72 |
| 10 | 141 |
| 11 | 280 |
| 12 | 516 |
| 13 | 976 |
| 14 | 1853 |
| 15 | 3420 |
| 16 | 6361 |
| 17 | 11844 |
| 18 | 21819 |
| 19 | 40192 |
| 20 | 73942 |
| 21 | 135452 |
| 22 | 247828 |
| 23 | 452776 |
| 24 | 825252 |
| 25 | 1501998 |
| 26 | 2730159 |
| 27 | 4954890 |
| 28 | 8981360 |
| 29 | 16261568 |
| 30 | 29408708 |
| 31 | 53130154 |
| 32 | 95894384 |
| 33 | 172917788 |
| 34 | 311538169 |
| 35 | 560831286 |
[1,0,3,6,7,20,42,72,141,280,516,976,1853,3420, 6361,11844,21819,40192,73942,135452,247828,452776, 825252,1501998,2730159,4954890,8981360,16261568, 29408708,53130154,95894384,172917788,311538169, 560831286] |