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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 20 |
| 2 | 20 |
| 3 | 40 |
| 4 | 60 |
| 5 | 100 |
| 6 | 160 |
| 7 | 260 |
| 8 | 420 |
| 9 | 680 |
| 10 | 1100 |
| 11 | 1780 |
| 12 | 2880 |
| 13 | 4660 |
| 14 | 7540 |
| 15 | 12200 |
| 16 | 19740 |
| 17 | 31940 |
| 18 | 51680 |
| 19 | 83620 |
| 20 | 135300 |
| 21 | 218920 |
| 22 | 354220 |
| 23 | 573140 |
| 24 | 927360 |
| 25 | 1500500 |
| 26 | 2427860 |
| 27 | 3928360 |
| 28 | 6356220 |
| 29 | 10284580 |
[0,20,20,40,60,100,160,260,420,680,1100,1780,2880, 4660,7540,12200,19740,31940,51680,83620,135300, 218920,354220,573140,927360,1500500,2427860, 3928360,6356220,10284580] |