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A087449 as a simple table
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 19 |
| 3 | 91 |
| 4 | 427 |
| 5 | 1963 |
| 6 | 8875 |
| 7 | 39595 |
| 8 | 174763 |
| 9 | 764587 |
| 10 | 3320491 |
| 11 | 14330539 |
| 12 | 61516459 |
| 13 | 262843051 |
| 14 | 1118481067 |
| 15 | 4742359723 |
| 16 | 20043180715 |
| 17 | 84467690155 |
| 18 | 355050629803 |
| 19 | 1488921995947 |
| 20 | 6230565890731 |
| 21 | 26021775190699 |
| 22 | 108485147273899 |
[1,4,19,91,427,1963,8875,39595,174763,764587, 3320491,14330539,61516459,262843051,1118481067, 4742359723,20043180715,84467690155,355050629803, 1488921995947,6230565890731,26021775190699, 108485147273899] |