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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 28 |
| 5 | 91 |
| 6 | 330 |
| 7 | 1158 |
| 8 | 4301 |
| 9 | 15704 |
| 10 | 59202 |
| 11 | 221160 |
| 12 | 842264 |
| 13 | 3192043 |
| 14 | 12246092 |
| 15 | 46861680 |
| 16 | 180776672 |
| 17 | 696518376 |
| 18 | 2698468580 |
| 19 | 10449533172 |
| 20 | 40622230498 |
| 21 | 157911491626 |
| 22 | 615583136488 |
| 23 | 2400206401102 |
| 24 | 9378223581365 |
| 25 | 36655425305228 |
| 26 | 143499450616324 |
| 27 | 561998883034538 |
| 28 | 2203752597514260 |
[1,1,3,8,28,91,330,1158,4301,15704,59202,221160, 842264,3192043,12246092,46861680,180776672, 696518376,2698468580,10449533172,40622230498, 157911491626,615583136488,2400206401102, 9378223581365,36655425305228,143499450616324, 561998883034538,2203752597514260] |