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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 26 |
| 5 | 104 |
| 6 | 402 |
| 7 | 1578 |
| 8 | 6196 |
| 9 | 24310 |
| 10 | 95446 |
| 11 | 374872 |
| 12 | 1472938 |
| 13 | 5790024 |
| 14 | 22768624 |
| 15 | 89562540 |
| 16 | 352395768 |
| 17 | 1386874908 |
| 18 | 5459330780 |
| 19 | 21494802570 |
| 20 | 84648191106 |
| 21 | 333419873528 |
| 22 | 1313575442496 |
| 23 | 5176174458602 |
| 24 | 20401118165166 |
| 25 | 80425006887898 |
[0,2,6,26,104,402,1578,6196,24310,95446,374872, 1472938,5790024,22768624,89562540,352395768, 1386874908,5459330780,21494802570,84648191106, 333419873528,1313575442496,5176174458602, 20401118165166,80425006887898] |