| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 47 |
| 5 | 164 |
| 6 | 695 |
| 7 | 2699 |
| 8 | 11928 |
| 9 | 48830 |
| 10 | 220914 |
| 11 | 940961 |
| 12 | 4321991 |
| 13 | 18937219 |
| 14 | 87972118 |
| 15 | 393301987 |
| 16 | 1843766751 |
| 17 | 8369121619 |
| 18 | 39519636049 |
| 19 | 181547249045 |
| 20 | 862251480517 |
| 21 | 3999666690154 |
| 22 | 19086139896338 |
| 23 | 89240905816222 |
| 24 | 427543488272411 |
| 25 | 2012304113539057 |
| 26 | 9673425072162760 |
| 27 | 45783191013294482 |
[1,1,4,12,47,164,695,2699,11928,48830,220914, 940961,4321991,18937219,87972118,393301987, 1843766751,8369121619,39519636049,181547249045, 862251480517,3999666690154,19086139896338, 89240905816222,427543488272411,2012304113539057, 9673425072162760,45783191013294482] |