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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 44 |
| 5 | 156 |
| 6 | 560 |
| 7 | 2065 |
| 8 | 7702 |
| 9 | 28898 |
| 10 | 109382 |
| 11 | 415768 |
| 12 | 1589470 |
| 13 | 6102378 |
| 14 | 23500260 |
| 15 | 90781393 |
| 16 | 351496758 |
| 17 | 1364024040 |
| 18 | 5303511032 |
| 19 | 20655297846 |
| 20 | 80569251748 |
| 21 | 314690828550 |
| 22 | 1230632550218 |
| 23 | 4817793313450 |
| 24 | 18879891033224 |
| 25 | 74053400563496 |
| 26 | 290704112428572 |
| 27 | 1142059574537634 |
| 28 | 4489837317690300 |
[1,1,4,13,44,156,560,2065,7702,28898,109382, 415768,1589470,6102378,23500260,90781393, 351496758,1364024040,5303511032,20655297846, 80569251748,314690828550,1230632550218, 4817793313450,18879891033224,74053400563496, 290704112428572,1142059574537634,4489837317690300] |