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 | 4 |
| 2 | 50 |
| 3 | 450 |
| 4 | 4590 |
| 5 | 45405 |
| 6 | 454950 |
| 7 | 4544550 |
| 8 | 45454500 |
| 9 | 454495500 |
| 10 | 4545045000 |
| 11 | 45449955000 |
| 12 | 454500450000 |
| 13 | 4544999550000 |
| 14 | 45450004500000 |
| 15 | 454499995500000 |
| 16 | 4545000045000000 |
| 17 | 45449999955000000 |
| 18 | 454500000450000000 |
| 19 | 4544999999550000000 |
| 20 | 45450000004500000000 |