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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 715 |
| 3 | 29393 |
| 4 | 1337220 |
| 5 | 64822395 |
| 6 | 3282060210 |
| 7 | 171529806825 |
| 8 | 9183676536076 |
| 9 | 501121108325684 |
| 10 | 27767032438524099 |
| 11 | 1558142747453650631 |
| 12 | 88366931393503350700 |
| 13 | 5056959295818949067010 |
| 14 | 291650059796498346544020 |
| 15 | 16934386878595523443214745 |
| 16 | 989130828878080326811887228 |
| 17 | 58078935727891217125276922940 |
| 18 | 3426228463922436748774829232156 |
| 19 | 202972497563788492865321721683556 |
[1,21,715,29393,1337220,64822395,3282060210, 171529806825,9183676536076,501121108325684, 27767032438524099,1558142747453650631, 88366931393503350700,5056959295818949067010, 291650059796498346544020, 16934386878595523443214745, 989130828878080326811887228, 58078935727891217125276922940, 3426228463922436748774829232156, 202972497563788492865321721683556] |