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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 18 |
| 5 | 56 |
| 6 | 191 |
| 7 | 640 |
| 8 | 2133 |
| 9 | 7141 |
| 10 | 23881 |
| 11 | 79850 |
| 12 | 267048 |
| 13 | 893051 |
| 14 | 2986496 |
| 15 | 9987385 |
| 16 | 33399513 |
| 17 | 111693661 |
| 18 | 373522786 |
| 19 | 1249124120 |
| 20 | 4177284903 |
| 21 | 13969556096 |
| 22 | 46716587501 |
| 23 | 156228267805 |
| 24 | 522454078593 |
| 25 | 1747175898106 |
| 26 | 5842855371016 |
| 27 | 19539508829315 |
| 28 | 65343463262208 |
[0,1,1,5,18,56,191,640,2133,7141,23881,79850, 267048,893051,2986496,9987385,33399513,111693661, 373522786,1249124120,4177284903,13969556096, 46716587501,156228267805,522454078593, 1747175898106,5842855371016,19539508829315, 65343463262208] |