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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 138 |
| 5 | 2202 |
| 6 | 44172 |
| 7 | 1064664 |
| 8 | 29947644 |
| 9 | 962720316 |
| 10 | 34812065304 |
| 11 | 1398413067984 |
| 12 | 61779789904248 |
| 13 | 2976866834860728 |
| 14 | 155364530441352912 |
| 15 | 8730749828092965408 |
| 16 | 525584335643810008848 |
| 17 | 33743905825099188235536 |
| 18 | 2301524700814009677800736 |
[1,1,2,12,138,2202,44172,1064664,29947644, 962720316,34812065304,1398413067984, 61779789904248,2976866834860728, 155364530441352912,8730749828092965408, 525584335643810008848,33743905825099188235536, 2301524700814009677800736] |