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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 13 |
| 4 | 53 |
| 5 | 267 |
| 6 | 1602 |
| 7 | 11216 |
| 8 | 89733 |
| 9 | 807604 |
| 10 | 8076042 |
| 11 | 88836472 |
| 12 | 1066037665 |
| 13 | 13858489652 |
| 14 | 194018855141 |
| 15 | 2910282827124 |
| 16 | 46564525233992 |
| 17 | 791596928977869 |
| 18 | 14248744721601653 |
| 19 | 270726149710431419 |
| 20 | 5414522994208628397 |
[2,4,13,53,267,1602,11216,89733,807604,8076042, 88836472,1066037665,13858489652,194018855141, 2910282827124,46564525233992,791596928977869, 14248744721601653,270726149710431419, 5414522994208628397] |