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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 10 |
| 3 | 42 |
| 4 | 235 |
| 5 | 1450 |
| 6 | 30883 |
| 7 | 267772 |
| 8 | 7073732 |
| 9 | 67911068 |
| 10 | 1835377464 |
| 11 | 17762404598 |
| 12 | 478005487727 |
| 13 | 4694125854134 |
| 14 | 124576004895424 |
| 15 | 1240340640828968 |
| 16 | 32486189811716076 |
| 17 | 327738319146833494 |
| 18 | 8473377832221877331 |
[4,10,42,235,1450,30883,267772,7073732,67911068, 1835377464,17762404598,478005487727,4694125854134, 124576004895424,1240340640828968, 32486189811716076,327738319146833494, 8473377832221877331] |