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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 44 |
| 4 | 311 |
| 5 | 2178 |
| 6 | 15250 |
| 7 | 106755 |
| 8 | 747288 |
| 9 | 5231022 |
| 10 | 36617161 |
| 11 | 256320132 |
| 12 | 1794240932 |
| 13 | 12559686533 |
| 14 | 87917805738 |
| 15 | 615424640176 |
| 16 | 4307972481243 |
| 17 | 30155807368710 |
| 18 | 211090651580982 |
| 19 | 1477634561066887 |
| 20 | 10343441927468220 |
[0,1,6,44,311,2178,15250,106755,747288,5231022, 36617161,256320132,1794240932,12559686533, 87917805738,615424640176,4307972481243, 30155807368710,211090651580982,1477634561066887, 10343441927468220] |