The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 12 |
| 3 | 36 |
| 4 | 102 |
| 5 | 288 |
| 6 | 816 |
| 7 | 2304 |
| 8 | 6510 |
| 9 | 18396 |
| 10 | 51972 |
| 11 | 146844 |
| 12 | 414894 |
| 13 | 1172232 |
| 14 | 3312024 |
| 15 | 9357768 |
| 16 | 26439366 |
| 17 | 74701620 |
| 18 | 211061436 |
| 19 | 596331540 |
| 20 | 1684871094 |
| 21 | 4760423280 |
| 22 | 13450067520 |
| 23 | 38001729168 |
| 24 | 107369826654 |
| 25 | 303361976844 |
[1,4,12,36,102,288,816,2304,6510,18396,51972, 146844,414894,1172232,3312024,9357768,26439366, 74701620,211061436,596331540,1684871094, 4760423280,13450067520,38001729168,107369826654, 303361976844] |