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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 18 |
| 3 | 63 |
| 4 | 221 |
| 5 | 776 |
| 6 | 2725 |
| 7 | 9569 |
| 8 | 33602 |
| 9 | 117995 |
| 10 | 414345 |
| 11 | 1454992 |
| 12 | 5109273 |
| 13 | 17941453 |
| 14 | 63002258 |
| 15 | 221235399 |
| 16 | 776878533 |
| 17 | 2728045592 |
| 18 | 9579660701 |
| 19 | 33639430153 |
| 20 | 118126444802 |
| 21 | 414806579603 |
| 22 | 1456612858961 |
| 23 | 5114964721440 |
| 24 | 17961439747441 |
| 25 | 63072442405845 |
| 26 | 221481854849938 |
| 27 | 777743974335503 |
| 28 | 2731084630047981 |
[1,5,18,63,221,776,2725,9569,33602,117995,414345, 1454992,5109273,17941453,63002258,221235399, 776878533,2728045592,9579660701,33639430153, 118126444802,414806579603,1456612858961, 5114964721440,17961439747441,63072442405845, 221481854849938,777743974335503,2731084630047981] |