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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 4 |
| 3 | 16 |
| 4 | 36 |
| 5 | 144 |
| 6 | 400 |
| 7 | 1600 |
| 8 | 4900 |
| 9 | 19600 |
| 10 | 63504 |
| 11 | 254016 |
| 12 | 853776 |
| 13 | 3415104 |
| 14 | 11778624 |
| 15 | 47114496 |
| 16 | 165636900 |
| 17 | 662547600 |
| 18 | 2363904400 |
| 19 | 9455617600 |
| 20 | 34134779536 |
| 21 | 136539118144 |
| 22 | 497634306624 |
| 23 | 1990537226496 |
| 24 | 7312459672336 |
[1,4,4,16,36,144,400,1600,4900,19600,63504,254016, 853776,3415104,11778624,47114496,165636900, 662547600,2363904400,9455617600,34134779536, 136539118144,497634306624,1990537226496, 7312459672336] |