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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 30 |
| 3 | 169 |
| 4 | 983 |
| 5 | 5701 |
| 6 | 33046 |
| 7 | 191692 |
| 8 | 1111756 |
| 9 | 6447926 |
| 10 | 37397230 |
| 11 | 216897344 |
| 12 | 1257968840 |
| 13 | 7296014816 |
| 14 | 42315682206 |
| 15 | 245424008900 |
| 16 | 1423418944526 |
| 17 | 8255595991972 |
| 18 | 47881100579920 |
| 19 | 277702517408082 |
| 20 | 1610628979299244 |
[4,30,169,983,5701,33046,191692,1111756,6447926, 37397230,216897344,1257968840,7296014816, 42315682206,245424008900,1423418944526, 8255595991972,47881100579920,277702517408082, 1610628979299244] |