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) |
|---|---|
| 1 | 1 |
| 2 | 9 |
| 3 | 45 |
| 4 | 999 |
| 5 | 2223 |
| 6 | 4950 |
| 7 | 5050 |
| 8 | 5292 |
| 9 | 7272 |
| 10 | 142857 |
| 11 | 148149 |
| 12 | 187110 |
| 13 | 356643 |
| 14 | 466830 |
| 15 | 499500 |
| 16 | 500500 |
| 17 | 538461 |
| 18 | 627615 |
| 19 | 648648 |
| 20 | 681318 |
| 21 | 791505 |
| 22 | 818181 |
| 23 | 961038 |
| 24 | 994708 |
| 25 | 5555556 |
| 26 | 11111112 |
| 27 | 16590564 |
| 28 | 30884184 |
| 29 | 36363636 |
| 30 | 49995000 |
| 31 | 50005000 |
| 32 | 55474452 |
| 33 | 74747475 |
| 34 | 234567901 |
| 35 | 432432432 |
| 36 | 665188470 |
| 37 | 999999999 |
| 38 | 2020202020 |
| 39 | 3846956652 |
| 40 | 4132841328 |
| 41 | 4999950000 |
| 42 | 5000050000 |