The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 127 |
| 3 | 168 |
| 4 | 1046 |
| 5 | 4583 |
| 6 | 17487 |
| 7 | 96175 |
| 8 | 534083 |
| 9 | 2689151 |
| 10 | 15357780 |
| 11 | 89959730 |
| 12 | 517714307 |
| 13 | 3063955854 |
| 14 | 18343096898 |
| 15 | 109721387508 |
| 16 | 660612374692 |
| 17 | 3991562407488 |
| 18 | 24145509389500 |
| 19 | 146334159352398 |
| 20 | 887846840631706 |
[21,127,168,1046,4583,17487,96175,534083,2689151, 15357780,89959730,517714307,3063955854, 18343096898,109721387508,660612374692, 3991562407488,24145509389500,146334159352398, 887846840631706] |