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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 30 |
| 5 | 90 |
| 6 | 308 |
| 7 | 963 |
| 8 | 3438 |
| 9 | 11234 |
| 10 | 39658 |
| 11 | 135300 |
| 12 | 485182 |
| 13 | 1661050 |
| 14 | 6059294 |
| 15 | 21080183 |
| 16 | 76433836 |
| 17 | 270898590 |
| 18 | 989797908 |
| 19 | 3508506050 |
| 20 | 12938529420 |
| 21 | 46251009992 |
| 22 | 169911558432 |
| 23 | 613777776976 |
| 24 | 2265122877620 |
| 25 | 8178540706698 |
| 26 | 30359539614762 |
| 27 | 110190927578014 |
| 28 | 407970567068040 |
| 29 | 1490764659238644 |
[1,1,4,9,30,90,308,963,3438,11234,39658,135300, 485182,1661050,6059294,21080183,76433836, 270898590,989797908,3508506050,12938529420, 46251009992,169911558432,613777776976, 2265122877620,8178540706698,30359539614762, 110190927578014,407970567068040,1490764659238644] |