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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 64 |
| 4 | 252 |
| 5 | 996 |
| 6 | 3936 |
| 7 | 15552 |
| 8 | 61452 |
| 9 | 242820 |
| 10 | 959472 |
| 11 | 3791232 |
| 12 | 14980572 |
| 13 | 59193828 |
| 14 | 233896896 |
| 15 | 924213888 |
| 16 | 3651913836 |
| 17 | 14430073860 |
| 18 | 57018604752 |
| 19 | 225301777344 |
| 20 | 890251367868 |
| 21 | 3517715249892 |
| 22 | 13899805185312 |
| 23 | 54923315409216 |
| 24 | 217022507533260 |
| 25 | 857536884383364 |
| 26 | 3388448121977520 |
| 27 | 13389022541682432 |
| 28 | 52905022644129948 |
| 29 | 209047479923369700 |
[1,4,16,64,252,996,3936,15552,61452,242820,959472, 3791232,14980572,59193828,233896896,924213888, 3651913836,14430073860,57018604752,225301777344, 890251367868,3517715249892,13899805185312, 54923315409216,217022507533260,857536884383364, 3388448121977520,13389022541682432, 52905022644129948,209047479923369700] |