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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 36 |
| 5 | 180 |
| 6 | 972 |
| 7 | 6300 |
| 8 | 44928 |
| 9 | 297432 |
| 10 | 1784592 |
| 11 | 10349856 |
| 12 | 60466176 |
| 13 | 358108128 |
| 14 | 2145709440 |
| 15 | 12958657344 |
| 16 | 78364164096 |
| 17 | 472093588224 |
| 18 | 2832129868032 |
| 19 | 16957996040448 |
| 20 | 101554796888064 |
| 21 | 608764662139392 |
| 22 | 3652587972836352 |
| 23 | 21926115464435712 |
| 24 | 131621703842267136 |
[1,4,9,36,180,972,6300,44928,297432,1784592, 10349856,60466176,358108128,2145709440, 12958657344,78364164096,472093588224, 2832129868032,16957996040448,101554796888064, 608764662139392,3652587972836352, 21926115464435712,131621703842267136] |