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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 21 |
| 3 | 201 |
| 4 | 1076 |
| 5 | 4025 |
| 6 | 11901 |
| 7 | 29841 |
| 8 | 66256 |
| 9 | 134001 |
| 10 | 251725 |
| 11 | 445401 |
| 12 | 750036 |
| 13 | 1211561 |
| 14 | 1888901 |
| 15 | 2856225 |
| 16 | 4205376 |
| 17 | 6048481 |
| 18 | 8520741 |
| 19 | 11783401 |
| 20 | 16026900 |
| 21 | 21474201 |
| 22 | 28384301 |
| 23 | 37055921 |
| 24 | 47831376 |
| 25 | 61100625 |
| 26 | 77305501 |
| 27 | 96944121 |
[1,21,201,1076,4025,11901,29841,66256,134001, 251725,445401,750036,1211561,1888901,2856225, 4205376,6048481,8520741,11783401,16026900, 21474201,28384301,37055921,47831376,61100625, 77305501,96944121] |