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 | 21 |
| 4 | 136 |
| 5 | 1045 |
| 6 | 9396 |
| 7 | 99379 |
| 8 | 1161952 |
| 9 | 14904873 |
| 10 | 208925380 |
| 11 | 3207759511 |
| 12 | 53349017184 |
| 13 | 950481426349 |
| 14 | 17959336305652 |
| 15 | 360094085423115 |
| 16 | 7656053670162496 |
| 17 | 172173524035504849 |
| 18 | 4077253037751090948 |
| 19 | 101263725993658291615 |
| 20 | 2627592803013505930240 |