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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 15 |
| 4 | 154 |
| 5 | 1115 |
| 6 | 5955 |
| 7 | 24836 |
| 8 | 85260 |
| 9 | 251154 |
| 10 | 655005 |
| 11 | 1548085 |
| 12 | 3374646 |
| 13 | 6876805 |
| 14 | 13237679 |
| 15 | 24271170 |
| 16 | 42667640 |
| 17 | 72305556 |
| 18 | 118640025 |
| 19 | 189179979 |
| 20 | 294066610 |
| 21 | 446766495 |
| 22 | 664893691 |
| 23 | 971175920 |
| 24 | 1394580804 |
| 25 | 1971618950 |
| 26 | 2747841525 |
| 27 | 3779550801 |
| 28 | 5135742990 |
| 29 | 6900303529 |
[0,1,15,154,1115,5955,24836,85260,251154,655005, 1548085,3374646,6876805,13237679,24271170, 42667640,72305556,118640025,189179979,294066610, 446766495,664893691,971175920,1394580804, 1971618950,2747841525,3779550801,5135742990, 6900303529] |