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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 40 |
| 5 | 122 |
| 6 | 468 |
| 7 | 1567 |
| 8 | 6112 |
| 9 | 21162 |
| 10 | 83196 |
| 11 | 296598 |
| 12 | 1170760 |
| 13 | 4259252 |
| 14 | 16858192 |
| 15 | 62189887 |
| 16 | 246726504 |
| 17 | 919595326 |
| 18 | 3654991076 |
| 19 | 13734831550 |
| 20 | 54659800248 |
| 21 | 206768895132 |
| 22 | 823609387928 |
| 23 | 3132526493386 |
| 24 | 12486623852344 |
| 25 | 47705231049608 |
| 26 | 190272793552880 |
| 27 | 729685146355196 |
| 28 | 2911758222803120 |
[1,1,4,11,40,122,468,1567,6112,21162,83196,296598, 1170760,4259252,16858192,62189887,246726504, 919595326,3654991076,13734831550,54659800248, 206768895132,823609387928,3132526493386, 12486623852344,47705231049608,190272793552880, 729685146355196,2911758222803120] |