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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 53 |
| 4 | 612 |
| 5 | 8676 |
| 6 | 145268 |
| 7 | 2798355 |
| 8 | 60852004 |
| 9 | 1472460760 |
| 10 | 39202586348 |
| 11 | 1138006266618 |
| 12 | 35750917265544 |
| 13 | 1207874695612336 |
| 14 | 43655110115967528 |
| 15 | 1680097198812367783 |
| 16 | 68578132320350944324 |
| 17 | 2958457556868808457800 |
| 18 | 134469635178557071054492 |
| 19 | 6421829932908536633173110 |
[1,1,6,53,612,8676,145268,2798355,60852004, 1472460760,39202586348,1138006266618, 35750917265544,1207874695612336,43655110115967528, 1680097198812367783,68578132320350944324, 2958457556868808457800,134469635178557071054492, 6421829932908536633173110] |