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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 23 |
| 4 | 155 |
| 5 | 1142 |
| 6 | 8910 |
| 7 | 72350 |
| 8 | 605056 |
| 9 | 5175866 |
| 10 | 45077560 |
| 11 | 398348733 |
| 12 | 3562916317 |
| 13 | 32192775763 |
| 14 | 293410452560 |
| 15 | 2694283228653 |
| 16 | 24902681767987 |
| 17 | 231496130358758 |
| 18 | 2162985033344112 |
| 19 | 20301976721356134 |
| 20 | 191336242071696514 |
| 21 | 1809916398759630481 |
| 22 | 17178063381786563194 |
| 23 | 163536967014934201972 |
| 24 | 1561247114394683682834 |
| 25 | 14943175106109268856975 |
[1,1,4,23,155,1142,8910,72350,605056,5175866, 45077560,398348733,3562916317,32192775763, 293410452560,2694283228653,24902681767987, 231496130358758,2162985033344112, 20301976721356134,191336242071696514, 1809916398759630481,17178063381786563194, 163536967014934201972,1561247114394683682834, 14943175106109268856975] |