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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 19 |
| 4 | 189 |
| 5 | 2576 |
| 6 | 44683 |
| 7 | 941977 |
| 8 | 23388025 |
| 9 | 668520163 |
| 10 | 21622993111 |
| 11 | 780789908240 |
| 12 | 31135480907413 |
| 13 | 1358965445353621 |
| 14 | 64440211018897379 |
| 15 | 3298807094967155971 |
| 16 | 181322497435007616497 |
| 17 | 10651131815012588324380 |
| 18 | 665881649529214120845679 |
| 19 | 44144097851022253967955749 |