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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 72 |
| 4 | 336 |
| 5 | 1568 |
| 6 | 7488 |
| 7 | 36160 |
| 8 | 174720 |
| 9 | 851456 |
| 10 | 4169728 |
| 11 | 20430848 |
| 12 | 100515840 |
| 13 | 495792128 |
| 14 | 2446532608 |
| 15 | 12099710976 |
| 16 | 59931222016 |
| 17 | 296944959488 |
| 18 | 1473274707968 |
| 19 | 7316502806528 |
| 20 | 36344236736512 |
| 21 | 180693350744064 |
| 22 | 898922565861376 |
| 23 | 4472907322884096 |
| 24 | 22269415918665728 |
| 25 | 110921723058061312 |
[1,4,16,72,336,1568,7488,36160,174720,851456, 4169728,20430848,100515840,495792128,2446532608, 12099710976,59931222016,296944959488, 1473274707968,7316502806528,36344236736512, 180693350744064,898922565861376,4472907322884096, 22269415918665728,110921723058061312] |