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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 18 |
| 5 | 73 |
| 6 | 255 |
| 7 | 950 |
| 8 | 3473 |
| 9 | 13006 |
| 10 | 48840 |
| 11 | 185353 |
| 12 | 706404 |
| 13 | 2706608 |
| 14 | 10404625 |
| 15 | 40126430 |
| 16 | 155133811 |
| 17 | 601119492 |
| 18 | 2333671638 |
| 19 | 9075290555 |
| 20 | 35345525798 |
| 21 | 137847145330 |
| 22 | 538258922839 |
| 23 | 2104101413400 |
| 24 | 8233434921693 |
| 25 | 32247613423563 |
| 26 | 126410623214720 |
| 27 | 495918571702575 |
[1,1,6,18,73,255,950,3473,13006,48840,185353, 706404,2706608,10404625,40126430,155133811, 601119492,2333671638,9075290555,35345525798, 137847145330,538258922839,2104101413400, 8233434921693,32247613423563,126410623214720, 495918571702575] |