The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 11 |
| 4 | 55 |
| 5 | 155 |
| 6 | 775 |
| 7 | 2461 |
| 8 | 12305 |
| 9 | 41937 |
| 10 | 209685 |
| 11 | 749109 |
| 12 | 3745545 |
| 13 | 13841585 |
| 14 | 69207925 |
| 15 | 262382303 |
| 16 | 1311911515 |
| 17 | 5074609495 |
| 18 | 25373047475 |
| 19 | 99750359987 |
| 20 | 498751799935 |
| 21 | 1987223356735 |
| 22 | 9936116783675 |
| 23 | 40038441228455 |
| 24 | 200192206142275 |
| 25 | 814502846723719 |
| 26 | 4072514233618595 |
| 27 | 16708181701724503 |
[1,1,5,11,55,155,775,2461,12305,41937,209685, 749109,3745545,13841585,69207925,262382303, 1311911515,5074609495,25373047475,99750359987, 498751799935,1987223356735,9936116783675, 40038441228455,200192206142275,814502846723719, 4072514233618595,16708181701724503] |