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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 92 |
| 4 | 628 |
| 5 | 4579 |
| 6 | 34917 |
| 7 | 275041 |
| 8 | 2220472 |
| 9 | 18275896 |
| 10 | 152780718 |
| 11 | 1293657534 |
| 12 | 11072033677 |
| 13 | 95629771059 |
| 14 | 832460471465 |
| 15 | 7296161486583 |
| 16 | 64331378963164 |
| 17 | 570228657335744 |
| 18 | 5078345448484216 |
| 19 | 45418278349485960 |
| 20 | 407749837317844851 |
| 21 | 3673300856466182388 |
[1,3,15,92,628,4579,34917,275041,2220472,18275896, 152780718,1293657534,11072033677,95629771059, 832460471465,7296161486583,64331378963164, 570228657335744,5078345448484216, 45418278349485960,407749837317844851, 3673300856466182388] |