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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 35 |
| 4 | 216 |
| 5 | 1575 |
| 6 | 13243 |
| 7 | 126508 |
| 8 | 1359437 |
| 9 | 16312915 |
| 10 | 217277446 |
| 11 | 3194459333 |
| 12 | 51557948291 |
| 13 | 908431129702 |
| 14 | 17376289236947 |
| 15 | 358847480175063 |
| 16 | 7959468559605624 |
| 17 | 188702262366570387 |
| 18 | 4760773506835189975 |
| 19 | 127312428854513811012 |
| 20 | 3596091234340397964321 |
[1,2,7,35,216,1575,13243,126508,1359437,16312915, 217277446,3194459333,51557948291,908431129702, 17376289236947,358847480175063,7959468559605624, 188702262366570387,4760773506835189975, 127312428854513811012,3596091234340397964321] |