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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 11 |
| 7 | 33 |
| 8 | 136 |
| 9 | 478 |
| 10 | 1849 |
| 11 | 6845 |
| 12 | 26136 |
| 13 | 98406 |
| 14 | 373977 |
| 15 | 1416249 |
| 16 | 5380770 |
| 17 | 20440250 |
| 18 | 77794939 |
| 19 | 296384565 |
| 20 | 1131009781 |
| 21 | 4321964735 |
| 22 | 16541268223 |
| 23 | 63400061153 |
| 24 | 243358777620 |
| 25 | 935431121460 |
| 26 | 3600520732809 |
[0,0,0,1,2,11,33,136,478,1849,6845,26136,98406, 373977,1416249,5380770,20440250,77794939, 296384565,1131009781,4321964735,16541268223, 63400061153,243358777620,935431121460, 3600520732809] |