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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 52 |
| 4 | 1004 |
| 5 | 24540 |
| 6 | 693528 |
| 7 | 21365548 |
| 8 | 694033712 |
| 9 | 23369007288 |
| 10 | 808414759404 |
| 11 | 28582681491280 |
| 12 | 1029170281603296 |
| 13 | 37633688114705676 |
| 14 | 1394397634883242504 |
| 15 | 52252719103306019248 |
| 16 | 1977346544751795430944 |
| 17 | 75468918458797503960180 |
| 18 | 2902157847756806886385760 |
| 19 | 112350085062188369503742656 |
[1,4,52,1004,24540,693528,21365548,694033712, 23369007288,808414759404,28582681491280, 1029170281603296,37633688114705676, 1394397634883242504,52252719103306019248, 1977346544751795430944,75468918458797503960180, 2902157847756806886385760, 112350085062188369503742656] |