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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 21 |
| 4 | 68 |
| 5 | 198 |
| 6 | 510 |
| 7 | 1248 |
| 8 | 2904 |
| 9 | 6393 |
| 10 | 13604 |
| 11 | 28044 |
| 12 | 55956 |
| 13 | 108982 |
| 14 | 207552 |
| 15 | 386622 |
| 16 | 707216 |
| 17 | 1271970 |
| 18 | 2250582 |
| 19 | 3925780 |
| 20 | 6757272 |
| 21 | 11483232 |
| 22 | 19290824 |
| 23 | 32057352 |
| 24 | 52722744 |
| 25 | 85884503 |
| 26 | 138644292 |
| 27 | 221885805 |
| 28 | 352241792 |
| 29 | 554892894 |
[1,6,21,68,198,510,1248,2904,6393,13604,28044, 55956,108982,207552,386622,707216,1271970,2250582, 3925780,6757272,11483232,19290824,32057352, 52722744,85884503,138644292,221885805,352241792, 554892894] |