The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 1 |
| 5 | 13 |
| 6 | 52 |
| 7 | 1 |
| 8 | 40 |
| 9 | 130 |
| 10 | 520 |
| 11 | 2080 |
| 12 | 1 |
| 13 | 121 |
| 14 | 1210 |
| 15 | 4840 |
| 16 | 15730 |
| 17 | 62920 |
| 18 | 251680 |
| 19 | 1 |
| 20 | 364 |
| 21 | 11011 |
| 22 | 33880 |
| 23 | 44044 |
| 24 | 440440 |
| 25 | 1431430 |
| 26 | 1761760 |
| 27 | 5725720 |
| 28 | 22902880 |
| 29 | 91611520 |
| 30 | 1 |
| 31 | 1093 |
| 32 | 99463 |
| 33 | 925771 |
| 34 | 397852 |
| 35 | 12035023 |
| 36 | 37030840 |
| 37 | 120350230 |
| 38 | 48140092 |
| 39 | 481400920 |
| 40 | 1564552990 |
[1,1,4,1,13,52,1,40,130,520,2080,1,121,1210,4840, 15730,62920,251680,1,364,11011,33880,44044,440440, 1431430,1761760,5725720,22902880,91611520,1,1093, 99463,925771,397852,12035023,37030840,120350230, 48140092,481400920,1564552990] |