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 | 1 |
| 2 | 4 |
| 3 | 27 |
| 4 | 252 |
| 5 | 2935 |
| 6 | 40351 |
| 7 | 633864 |
| 8 | 11139840 |
| 9 | 215800335 |
| 10 | 4557031407 |
| 11 | 103989209082 |
| 12 | 2546369980589 |
| 13 | 66521801043100 |
| 14 | 1845008781481516 |
| 15 | 54102505102771686 |
| 16 | 1671315770146956704 |
| 17 | 54219694639758864087 |
| 18 | 1842085959295755494339 |
| 19 | 65380444351870047159358 |