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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 25 |
| 6 | 91 |
| 7 | 322 |
| 8 | 1232 |
| 9 | 5672 |
| 10 | 32202 |
| 11 | 209143 |
| 12 | 1432454 |
| 13 | 9942517 |
| 14 | 69363840 |
| 15 | 490303335 |
| 16 | 3565609732 |
| 17 | 27118060170 |
| 18 | 218183781871 |
| 19 | 1861370544934 |
| 20 | 16729411124821 |
| 21 | 156706028787827 |
| 22 | 1514442896327792 |
| 23 | 14999698898942772 |
| 24 | 151838974745743228 |
| 25 | 1571513300578303070 |
[1,0,0,1,6,25,91,322,1232,5672,32202,209143, 1432454,9942517,69363840,490303335,3565609732, 27118060170,218183781871,1861370544934, 16729411124821,156706028787827,1514442896327792, 14999698898942772,151838974745743228, 1571513300578303070] |