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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 18 |
| 4 | 153 |
| 5 | 770 |
| 6 | 2859 |
| 7 | 8694 |
| 8 | 22924 |
| 9 | 54272 |
| 10 | 118057 |
| 11 | 239798 |
| 12 | 460207 |
| 13 | 841930 |
| 14 | 1478451 |
| 15 | 2505634 |
| 16 | 4116442 |
| 17 | 6579440 |
| 18 | 10261761 |
| 19 | 15657290 |
| 20 | 23420901 |
| 21 | 34409666 |
| 22 | 49732043 |
| 23 | 70806142 |
| 24 | 99428264 |
| 25 | 137853008 |
| 26 | 188886345 |
| 27 | 255993166 |
| 28 | 343420923 |
[0,1,18,153,770,2859,8694,22924,54272,118057, 239798,460207,841930,1478451,2505634,4116442, 6579440,10261761,15657290,23420901,34409666, 49732043,70806142,99428264,137853008,188886345, 255993166,343420923] |