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 | 116 |
| 5 | 344 |
| 6 | 1104 |
| 7 | 3280 |
| 8 | 10456 |
| 9 | 31152 |
| 10 | 98804 |
| 11 | 295988 |
| 12 | 935876 |
| 13 | 2811540 |
| 14 | 8870324 |
| 15 | 26695724 |
| 16 | 84060148 |
| 17 | 253376840 |
| 18 | 796635360 |
| 19 | 2404558304 |
| 20 | 7549431884 |
| 21 | 22820942416 |
| 22 | 71541295984 |
| 23 | 216562743948 |
| 24 | 677938097756 |
| 25 | 2054922521644 |
[1,4,12,36,116,344,1104,3280,10456,31152,98804, 295988,935876,2811540,8870324,26695724,84060148, 253376840,796635360,2404558304,7549431884, 22820942416,71541295984,216562743948,677938097756, 2054922521644] |