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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 19 |
| 2 | 90 |
| 3 | 426 |
| 4 | 2016 |
| 5 | 9541 |
| 6 | 45154 |
| 7 | 213697 |
| 8 | 1011348 |
| 9 | 4786332 |
| 10 | 22651920 |
| 11 | 107203069 |
| 12 | 507352048 |
| 13 | 2401107571 |
| 14 | 11363544486 |
| 15 | 53779407822 |
| 16 | 254517831936 |
| 17 | 1204537747753 |
| 18 | 5700626846950 |
| 19 | 26978935702753 |
| 20 | 127681216679304 |
| 21 | 604267465267128 |
| 22 | 2859772009358880 |
| 23 | 13534231802298265 |
| 24 | 64052459384483260 |
| 25 | 303136344428812723 |
| 26 | 1434630991482656082 |
| 27 | 6789572149788327282 |
[4,19,90,426,2016,9541,45154,213697,1011348, 4786332,22651920,107203069,507352048,2401107571, 11363544486,53779407822,254517831936, 1204537747753,5700626846950,26978935702753, 127681216679304,604267465267128,2859772009358880, 13534231802298265,64052459384483260, 303136344428812723,1434630991482656082, 6789572149788327282] |