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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 10 |
| 4 | 24 |
| 5 | 54 |
| 6 | 116 |
| 7 | 250 |
| 8 | 528 |
| 9 | 1118 |
| 10 | 2348 |
| 11 | 4930 |
| 12 | 10312 |
| 13 | 21542 |
| 14 | 44900 |
| 15 | 93450 |
| 16 | 194176 |
| 17 | 402926 |
| 18 | 834972 |
| 19 | 1728210 |
| 20 | 3572920 |
| 21 | 7378870 |
| 22 | 15223764 |
| 23 | 31379610 |
| 24 | 64623344 |
| 25 | 132974974 |
| 26 | 273406476 |
| 27 | 561726050 |
| 28 | 1153278248 |
| 29 | 2366208838 |
| 30 | 4851722308 |
[0,4,10,24,54,116,250,528,1118,2348,4930,10312, 21542,44900,93450,194176,402926,834972,1728210, 3572920,7378870,15223764,31379610,64623344, 132974974,273406476,561726050,1153278248, 2366208838,4851722308] |