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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 52 |
| 5 | 185 |
| 6 | 835 |
| 7 | 3281 |
| 8 | 15158 |
| 9 | 63309 |
| 10 | 296887 |
| 11 | 1289845 |
| 12 | 6111674 |
| 13 | 27277697 |
| 14 | 130232632 |
| 15 | 592619901 |
| 16 | 2845730366 |
| 17 | 13138353029 |
| 18 | 63376378401 |
| 19 | 295889267987 |
| 20 | 1432525057484 |
| 21 | 6747494887431 |
| 22 | 32765754206296 |
| 23 | 155437488129585 |
| 24 | 756701050408249 |
| 25 | 3610745322320158 |
| 26 | 17615328569640258 |
| 27 | 84463982275069381 |
[1,1,4,12,52,185,835,3281,15158,63309,296887, 1289845,6111674,27277697,130232632,592619901, 2845730366,13138353029,63376378401,295889267987, 1432525057484,6747494887431,32765754206296, 155437488129585,756701050408249,3610745322320158, 17615328569640258,84463982275069381] |