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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 1 |
| 3 | 12 |
| 4 | 31 |
| 5 | 69 |
| 6 | 181 |
| 7 | 443 |
| 8 | 1052 |
| 9 | 2701 |
| 10 | 6455 |
| 11 | 15928 |
| 12 | 40073 |
| 13 | 100362 |
| 14 | 251707 |
| 15 | 637235 |
| 16 | 1617175 |
| 17 | 4124437 |
| 18 | 10553415 |
| 19 | 27066974 |
| 20 | 69709680 |
| 21 | 179992909 |
| 22 | 465769803 |
| 23 | 1208198526 |
| 24 | 3140421716 |
| 25 | 8179002096 |
| 26 | 21338685407 |
| 27 | 55762149030 |
| 28 | 145935689361 |
[2,1,12,31,69,181,443,1052,2701,6455,15928,40073, 100362,251707,637235,1617175,4124437,10553415, 27066974,69709680,179992909,465769803,1208198526, 3140421716,8179002096,21338685407,55762149030, 145935689361] |