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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 66 |
| 5 | 279 |
| 6 | 1201 |
| 7 | 5242 |
| 8 | 23133 |
| 9 | 103015 |
| 10 | 462269 |
| 11 | 2088146 |
| 12 | 9487405 |
| 13 | 43328580 |
| 14 | 198798447 |
| 15 | 915950385 |
| 16 | 4236322720 |
| 17 | 19661850045 |
| 18 | 91549502656 |
| 19 | 427539667095 |
| 20 | 2002120576312 |
| 21 | 9399659155395 |
| 22 | 44234927105888 |
| 23 | 208631813215116 |
[1,4,16,66,279,1201,5242,23133,103015,462269, 2088146,9487405,43328580,198798447,915950385, 4236322720,19661850045,91549502656,427539667095, 2002120576312,9399659155395,44234927105888, 208631813215116] |