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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 26 |
| 3 | 144 |
| 4 | 861 |
| 5 | 5300 |
| 6 | 33974 |
| 7 | 226716 |
| 8 | 1572134 |
| 9 | 11318196 |
| 10 | 84460828 |
| 11 | 652359324 |
| 12 | 5207769776 |
| 13 | 42909334344 |
| 14 | 364439847976 |
| 15 | 3186742207624 |
| 16 | 28656418042704 |
| 17 | 264722157073936 |
| 18 | 2509700822675234 |
| 19 | 24395793491141136 |
| 20 | 242936835660951240 |
| 21 | 2476311278424167804 |
| 22 | 25817877582760234776 |
| 23 | 275124609022178797944 |
| 24 | 2994612410107793787156 |
| 25 | 33272066553220515090708 |
| 26 | 377127538637173442895684 |
| 27 | 4358346743099457288466696 |
[1,4,26,144,861,5300,33974,226716,1572134, 11318196,84460828,652359324,5207769776, 42909334344,364439847976,3186742207624, 28656418042704,264722157073936,2509700822675234, 24395793491141136,242936835660951240, 2476311278424167804,25817877582760234776, 275124609022178797944,2994612410107793787156, 33272066553220515090708,377127538637173442895684, 4358346743099457288466696] |