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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 31 |
| 3 | 338 |
| 4 | 4356 |
| 5 | 61603 |
| 6 | 923958 |
| 7 | 14433315 |
| 8 | 232298914 |
| 9 | 3825260332 |
| 10 | 64140203645 |
| 11 | 1091364139213 |
| 12 | 18796605318655 |
| 13 | 327056343952311 |
| 14 | 5740466392321499 |
| 15 | 101516213938082457 |
| 16 | 1807045676161156515 |
| 17 | 32352346658163940698 |
| 18 | 582185299986049977601 |
| 19 | 10524395285312191583304 |
| 20 | 191034444423571726099486 |
[1,4,31,338,4356,61603,923958,14433315,232298914, 3825260332,64140203645,1091364139213, 18796605318655,327056343952311,5740466392321499, 101516213938082457,1807045676161156515, 32352346658163940698,582185299986049977601, 10524395285312191583304,191034444423571726099486] |