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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 31 |
| 3 | 141 |
| 4 | 506 |
| 5 | 1590 |
| 6 | 4593 |
| 7 | 12523 |
| 8 | 32740 |
| 9 | 82908 |
| 10 | 204755 |
| 11 | 495561 |
| 12 | 1179582 |
| 13 | 2768818 |
| 14 | 6422437 |
| 15 | 14745495 |
| 16 | 33554312 |
| 17 | 75759480 |
| 18 | 169869159 |
| 19 | 378535765 |
| 20 | 838860610 |
| 21 | 1849687854 |
| 22 | 4060086041 |
| 23 | 8875147011 |
| 24 | 19327352556 |
| 25 | 41943039700 |
[0,4,31,141,506,1590,4593,12523,32740,82908, 204755,495561,1179582,2768818,6422437,14745495, 33554312,75759480,169869159,378535765,838860610, 1849687854,4060086041,8875147011,19327352556, 41943039700] |