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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 21 |
| 3 | 143 |
| 4 | 1063 |
| 5 | 8385 |
| 6 | 68929 |
| 7 | 584467 |
| 8 | 5074924 |
| 9 | 44885325 |
| 10 | 402777151 |
| 11 | 3656032622 |
| 12 | 33492393634 |
| 13 | 309106153431 |
| 14 | 2870123507479 |
| 15 | 26783122426197 |
| 16 | 250971797533095 |
| 17 | 2359952229466124 |
| 18 | 22256979400698116 |
| 19 | 210440626023838163 |
| 20 | 1994088284872617955 |
| 21 | 18931694933036811169 |
[4,21,143,1063,8385,68929,584467,5074924,44885325, 402777151,3656032622,33492393634,309106153431, 2870123507479,26783122426197,250971797533095, 2359952229466124,22256979400698116, 210440626023838163,1994088284872617955, 18931694933036811169] |