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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 20 |
| 5 | 110 |
| 6 | 638 |
| 7 | 3828 |
| 8 | 23515 |
| 9 | 146970 |
| 10 | 930820 |
| 11 | 5957325 |
| 12 | 38452405 |
| 13 | 249944939 |
| 14 | 1634287025 |
| 15 | 10739831400 |
| 16 | 70884562683 |
| 17 | 469622328252 |
| 18 | 3121694320866 |
| 19 | 20811920304961 |
| 20 | 139115729296575 |
| 21 | 932107335003790 |
| 22 | 6258662787526655 |
| 23 | 42105353650697301 |
| 24 | 283765005631661148 |
| 25 | 1915495724241980280 |
| 26 | 12949332513585521217 |
| 27 | 87661142189041380207 |
| 28 | 594176943178375193748 |
| 29 | 4032121696383579351905 |
| 30 | 27392082325012470506385 |
| 31 | 186276500908841717917320 |
[1,1,4,20,110,638,3828,23515,146970,930820, 5957325,38452405,249944939,1634287025,10739831400, 70884562683,469622328252,3121694320866, 20811920304961,139115729296575,932107335003790, 6258662787526655,42105353650697301, 283765005631661148,1915495724241980280, 12949332513585521217,87661142189041380207, 594176943178375193748,4032121696383579351905, 27392082325012470506385,186276500908841717917320] |