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| n | a(n) |
|---|---|
| 1 | 7 |
| 2 | 18 |
| 3 | 60 |
| 4 | 168 |
| 5 | 528 |
| 6 | 1536 |
| 7 | 4704 |
| 8 | 13920 |
| 9 | 42144 |
| 10 | 125664 |
| 11 | 378528 |
| 12 | 1132512 |
| 13 | 3403680 |
| 14 | 10198752 |
| 15 | 30620832 |
| 16 | 91813344 |
| 17 | 275538336 |
| 18 | 826418400 |
| 19 | 2479648416 |
| 20 | 7438158816 |
| 21 | 22316049312 |
| 22 | 66945002208 |
| 23 | 200841298080 |
| 24 | 602511311328 |
| 25 | 1807559099808 |
[7,18,60,168,528,1536,4704,13920,42144,125664, 378528,1132512,3403680,10198752,30620832,91813344, 275538336,826418400,2479648416,7438158816, 22316049312,66945002208,200841298080,602511311328, 1807559099808] |