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 | 7 |
| 3 | 52 |
| 4 | 432 |
| 5 | 3878 |
| 6 | 36694 |
| 7 | 360498 |
| 8 | 3642534 |
| 9 | 37613947 |
| 10 | 395204413 |
| 11 | 4211469308 |
| 12 | 45409525116 |
| 13 | 494500127617 |
| 14 | 5430864937915 |
| 15 | 60083846523038 |
| 16 | 669005596426438 |
| 17 | 7491245872785003 |
| 18 | 84305386452532885 |
| 19 | 953020276395635246 |
| 20 | 10816782722212619970 |
| 21 | 123218274878407738497 |