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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 25 |
| 4 | 99 |
| 5 | 402 |
| 6 | 1687 |
| 7 | 7242 |
| 8 | 31589 |
| 9 | 139772 |
| 10 | 625245 |
| 11 | 2822337 |
| 12 | 12844579 |
| 13 | 58831382 |
| 14 | 271083007 |
| 15 | 1255384097 |
| 16 | 5839684171 |
| 17 | 27274710988 |
| 18 | 127836802627 |
| 19 | 601121704001 |
| 20 | 2834831034433 |
| 21 | 13404061945834 |
| 22 | 63533284212965 |
| 23 | 301801144126542 |
| 24 | 1436577862779165 |
| 25 | 6850988243782724 |
| 26 | 32728987989031165 |
| 27 | 156608974105107061 |
[1,2,7,25,99,402,1687,7242,31589,139772,625245, 2822337,12844579,58831382,271083007,1255384097, 5839684171,27274710988,127836802627,601121704001, 2834831034433,13404061945834,63533284212965, 301801144126542,1436577862779165,6850988243782724, 32728987989031165,156608974105107061] |