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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 67 |
| 4 | 304 |
| 5 | 1519 |
| 6 | 8386 |
| 7 | 51007 |
| 8 | 340024 |
| 9 | 2469859 |
| 10 | 19438606 |
| 11 | 164899447 |
| 12 | 1500636844 |
| 13 | 14587478299 |
| 14 | 150891959026 |
| 15 | 1655133221887 |
| 16 | 19192311085264 |
| 17 | 234597922978339 |
| 18 | 3015167371458646 |
| 19 | 40651421300224327 |
| 20 | 573707768015267284 |
| 21 | 8458761578948943979 |
| 22 | 130059537979390701466 |
[1,4,16,67,304,1519,8386,51007,340024,2469859, 19438606,164899447,1500636844,14587478299, 150891959026,1655133221887,19192311085264, 234597922978339,3015167371458646, 40651421300224327,573707768015267284, 8458761578948943979,130059537979390701466] |