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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 5 |
| 3 | 7 |
| 4 | 44 |
| 5 | 45 |
| 6 | 47 |
| 7 | 54 |
| 8 | 55 |
| 9 | 57 |
| 10 | 74 |
| 11 | 75 |
| 12 | 77 |
| 13 | 444 |
| 14 | 445 |
| 15 | 447 |
| 16 | 454 |
| 17 | 455 |
| 18 | 457 |
| 19 | 474 |
| 20 | 475 |
| 21 | 477 |
| 22 | 544 |
| 23 | 545 |
| 24 | 547 |
| 25 | 554 |
| 26 | 555 |
| 27 | 557 |
| 28 | 574 |
| 29 | 575 |
| 30 | 577 |
| 31 | 744 |
| 32 | 745 |
| 33 | 747 |
| 34 | 754 |
| 35 | 755 |
| 36 | 757 |
| 37 | 774 |
| 38 | 775 |
| 39 | 777 |
| 40 | 4444 |
| 41 | 4445 |
| 42 | 4447 |
| 43 | 4454 |
| 44 | 4455 |
| 45 | 4457 |
| 46 | 4474 |
| 47 | 4475 |
| 48 | 4477 |
| 49 | 4544 |
| 50 | 4545 |
| 51 | 4547 |
| 52 | 4554 |
| 53 | 4555 |
| 54 | 4557 |
| 55 | 4574 |
| 56 | 4575 |
| 57 | 4577 |
| 58 | 4744 |
[4,5,7,44,45,47,54,55,57,74,75,77,444,445,447,454, 455,457,474,475,477,544,545,547,554,555,557,574, 575,577,744,745,747,754,755,757,774,775,777,4444, 4445,4447,4454,4455,4457,4474,4475,4477,4544,4545, 4547,4554,4555,4557,4574,4575,4577,4744] |