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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 48 |
| 5 | 177 |
| 6 | 737 |
| 7 | 3029 |
| 8 | 12988 |
| 9 | 56091 |
| 10 | 246868 |
| 11 | 1096597 |
| 12 | 4924501 |
| 13 | 22280718 |
| 14 | 101576635 |
| 15 | 465761626 |
| 16 | 2147731327 |
| 17 | 9949376489 |
| 18 | 46289161625 |
| 19 | 216169270117 |
| 20 | 1012953446513 |
| 21 | 4761286903537 |
| 22 | 22442684861765 |
| 23 | 106056033165046 |
| 24 | 502360129027589 |
| 25 | 2384677778156798 |
| 26 | 11342524317323837 |
| 27 | 54049170686961451 |
[1,1,4,12,48,177,737,3029,12988,56091,246868, 1096597,4924501,22280718,101576635,465761626, 2147731327,9949376489,46289161625,216169270117, 1012953446513,4761286903537,22442684861765, 106056033165046,502360129027589,2384677778156798, 11342524317323837,54049170686961451] |