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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 23 |
| 3 | 100 |
| 4 | 435 |
| 5 | 1959 |
| 6 | 8872 |
| 7 | 40080 |
| 8 | 181116 |
| 9 | 818827 |
| 10 | 3702099 |
| 11 | 16737863 |
| 12 | 75676531 |
| 13 | 342158969 |
| 14 | 1547018148 |
| 15 | 6994611112 |
| 16 | 31625128427 |
| 17 | 142988537981 |
| 18 | 646502561252 |
| 19 | 2923070791847 |
| 20 | 13216256140714 |
| 21 | 59755457387534 |
| 22 | 270175964460613 |
[4,23,100,435,1959,8872,40080,181116,818827, 3702099,16737863,75676531,342158969,1547018148, 6994611112,31625128427,142988537981,646502561252, 2923070791847,13216256140714,59755457387534, 270175964460613] |