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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 8 |
| 4 | 20 |
| 5 | 37 |
| 6 | 86 |
| 7 | 173 |
| 8 | 372 |
| 9 | 788 |
| 10 | 1680 |
| 11 | 3550 |
| 12 | 7554 |
| 13 | 15994 |
| 14 | 33820 |
| 15 | 71374 |
| 16 | 150376 |
| 17 | 316151 |
| 18 | 663474 |
| 19 | 1389760 |
| 20 | 2906116 |
| 21 | 6066899 |
| 22 | 12645608 |
| 23 | 26318870 |
| 24 | 54700044 |
| 25 | 113536171 |
| 26 | 235363832 |
| 27 | 487342781 |
| 28 | 1007969620 |
| 29 | 2082597193 |
| 30 | 4298660754 |
[1,4,8,20,37,86,173,372,788,1680,3550,7554,15994, 33820,71374,150376,316151,663474,1389760,2906116, 6066899,12645608,26318870,54700044,113536171, 235363832,487342781,1007969620,2082597193, 4298660754] |