This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 22 |
| 3 | 33 |
| 4 | 44 |
| 5 | 55 |
| 6 | 66 |
| 7 | 77 |
| 8 | 88 |
| 9 | 99 |
| 10 | 1111 |
| 11 | -1 |
| 12 | 2552 |
| 13 | -1 |
| 14 | 2662 |
| 15 | 3443 |
| 16 | 2772 |
| 17 | -1 |
| 18 | 2882 |
| 19 | -1 |
| 20 | 2992 |
| 21 | 3663 |
| 22 | -1 |
| 23 | -1 |
| 24 | 3773 |
| 25 | 5445 |
| 26 | -1 |
| 27 | 3883 |
| 28 | 4664 |
| 29 | -1 |
| 30 | 3993 |
| 31 | -1 |
| 32 | 4774 |
| 33 | -1 |
| 34 | -1 |
| 35 | 5665 |
| 36 | 4884 |
| 37 | -1 |
| 38 | -1 |
| 39 | -1 |
| 40 | 4994 |
| 41 | -1 |
| 42 | 6666 |
| 43 | -1 |
| 44 | -1 |
| 45 | 5885 |
| 46 | -1 |
| 47 | -1 |
| 48 | 6776 |
| 49 | 7667 |
| 50 | 5995 |
| 51 | -1 |
| 52 | -1 |
| 53 | -1 |
| 54 | 6886 |