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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 55 |
| 3 | 57 |
| 4 | 74 |
| 5 | 77 |
| 6 | 445 |
| 7 | 447 |
| 8 | 454 |
| 9 | 545 |
| 10 | 554 |
| 11 | 745 |
| 12 | 755 |
| 13 | 4474 |
| 14 | 4555 |
| 15 | 4574 |
| 16 | 4577 |
| 17 | 4747 |
| 18 | 4754 |
| 19 | 4757 |
| 20 | 4777 |
| 21 | 5447 |
| 22 | 5455 |
| 23 | 5545 |
| 24 | 5554 |
| 25 | 5747 |
| 26 | 5755 |
| 27 | 5774 |
| 28 | 5777 |
| 29 | 7445 |
| 30 | 7447 |
| 31 | 7454 |
| 32 | 7555 |
| 33 | 7745 |
| 34 | 7747 |
| 35 | 7754 |
| 36 | 44477 |
| 37 | 44554 |
| 38 | 44557 |
| 39 | 44747 |
| 40 | 44755 |
| 41 | 45447 |
| 42 | 45454 |
| 43 | 45455 |
| 44 | 45457 |
[4,55,57,74,77,445,447,454,545,554,745,755,4474, 4555,4574,4577,4747,4754,4757,4777,5447,5455,5545, 5554,5747,5755,5774,5777,7445,7447,7454,7555,7745, 7747,7754,44477,44554,44557,44747,44755,45447, 45454,45455,45457] |