| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 73 |
| 5 | 621 |
| 6 | 6211 |
| 7 | 70393 |
| 8 | 884913 |
| 9 | 12534553 |
| 10 | 197772931 |
| 11 | 3429365061 |
| 12 | 64519103353 |
| 13 | 1309062244933 |
| 14 | 28518573321603 |
| 15 | 664268130978481 |
| 16 | 16466530506866401 |
| 17 | 432644339697987633 |
| 18 | 12007970879629419523 |
| 19 | 351062850914762411773 |
| 20 | 10783262700644774606121 |
[1,1,3,13,73,621,6211,70393,884913,12534553, 197772931,3429365061,64519103353,1309062244933, 28518573321603,664268130978481,16466530506866401, 432644339697987633,12007970879629419523, 351062850914762411773,10783262700644774606121] |