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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 170 |
| 3 | 970 |
| 4 | 4410 |
| 5 | 17172 |
| 6 | 59545 |
| 7 | 188700 |
| 8 | 556085 |
| 9 | 1542640 |
| 10 | 4065868 |
| 11 | 10253720 |
| 12 | 24880705 |
| 13 | 58351000 |
| 14 | 132750390 |
| 15 | 293867786 |
| 16 | 634623035 |
| 17 | 1339924290 |
| 18 | 2771178885 |
| 19 | 5623152080 |
| 20 | 11211087225 |
| 21 | 21989506510 |
| 22 | 42478375740 |
| 23 | 80897833810 |
| 24 | 152022961870 |
| 25 | 282119268256 |
| 26 | 517394696690 |
[1,20,170,970,4410,17172,59545,188700,556085, 1542640,4065868,10253720,24880705,58351000, 132750390,293867786,634623035,1339924290, 2771178885,5623152080,11211087225,21989506510, 42478375740,80897833810,152022961870,282119268256, 517394696690] |