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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 72 |
| 4 | 288 |
| 5 | 1168 |
| 6 | 5184 |
| 7 | 20768 |
| 8 | 85120 |
| 9 | 373312 |
| 10 | 1499392 |
| 11 | 6194304 |
| 12 | 26890752 |
| 13 | 108349696 |
| 14 | 450216960 |
| 15 | 1937707520 |
| 16 | 7834814464 |
| 17 | 32689300480 |
| 18 | 139682910208 |
| 19 | 566806726656 |
| 20 | 2371481051136 |
| 21 | 10073319706624 |
| 22 | 41018592608256 |
[1,4,16,72,288,1168,5184,20768,85120,373312, 1499392,6194304,26890752,108349696,450216960, 1937707520,7834814464,32689300480,139682910208, 566806726656,2371481051136,10073319706624, 41018592608256] |