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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 52 |
| 5 | 200 |
| 6 | 906 |
| 7 | 3835 |
| 8 | 17835 |
| 9 | 79215 |
| 10 | 374381 |
| 11 | 1710234 |
| 12 | 8170299 |
| 13 | 38011835 |
| 14 | 182943410 |
| 15 | 862048941 |
| 16 | 4171224246 |
| 17 | 19838535950 |
| 18 | 96382566615 |
| 19 | 461629848142 |
| 20 | 2249821353330 |
| 21 | 10834620431069 |
| 22 | 52936934322254 |
| 23 | 256041710688572 |
| 24 | 1253562592466569 |
| 25 | 6084551109301534 |
| 26 | 29840382820005767 |
| 27 | 145261082306545356 |
[1,1,4,12,52,200,906,3835,17835,79215,374381, 1710234,8170299,38011835,182943410,862048941, 4171224246,19838535950,96382566615,461629848142, 2249821353330,10834620431069,52936934322254, 256041710688572,1253562592466569,6084551109301534, 29840382820005767,145261082306545356] |