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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 72 |
| 4 | 336 |
| 5 | 1580 |
| 6 | 7574 |
| 7 | 36598 |
| 8 | 177752 |
| 9 | 868704 |
| 10 | 4258402 |
| 11 | 20936128 |
| 12 | 103202090 |
| 13 | 509559842 |
| 14 | 2520187796 |
| 15 | 12481010184 |
| 16 | 61875264382 |
| 17 | 307056555384 |
| 18 | 1524967205316 |
| 19 | 7578821252920 |
| 20 | 37688896375138 |
| 21 | 187520140021006 |
| 22 | 933438702735224 |
| 23 | 4648385161985330 |
| 24 | 23156509718095598 |
| 25 | 115394598227196336 |
[1,4,16,72,336,1580,7574,36598,177752,868704, 4258402,20936128,103202090,509559842,2520187796, 12481010184,61875264382,307056555384, 1524967205316,7578821252920,37688896375138, 187520140021006,933438702735224,4648385161985330, 23156509718095598,115394598227196336] |