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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 13 |
| 4 | 52 |
| 5 | 221 |
| 6 | 949 |
| 7 | 4056 |
| 8 | 17186 |
| 9 | 72163 |
| 10 | 300482 |
| 11 | 1241981 |
| 12 | 5100758 |
| 13 | 20833813 |
| 14 | 84695026 |
| 15 | 342920942 |
| 16 | 1383646433 |
| 17 | 5566235714 |
| 18 | 22334785486 |
| 19 | 89420529809 |
| 20 | 357319721889 |
| 21 | 1425447435997 |
| 22 | 5678246483273 |
| 23 | 22590565547134 |
| 24 | 89775857333032 |
| 25 | 356428030609222 |
| 26 | 1413891596961194 |
| 27 | 5604509198580578 |
[2,4,13,52,221,949,4056,17186,72163,300482, 1241981,5100758,20833813,84695026,342920942, 1383646433,5566235714,22334785486,89420529809, 357319721889,1425447435997,5678246483273, 22590565547134,89775857333032,356428030609222, 1413891596961194,5604509198580578] |