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 | 4 |
| 2 | 19 |
| 3 | 103 |
| 4 | 598 |
| 5 | 3601 |
| 6 | 22165 |
| 7 | 138445 |
| 8 | 873916 |
| 9 | 5560741 |
| 10 | 35605756 |
| 11 | 229142476 |
| 12 | 1480820176 |
| 13 | 9603245620 |
| 14 | 62463474700 |
| 15 | 407330900284 |
| 16 | 2662179813931 |
| 17 | 17433248900656 |
| 18 | 114359597479261 |
| 19 | 751343566800961 |
| 20 | 4943188072606456 |