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 | 3 |
| 2 | 21 |
| 3 | 219 |
| 4 | 2973 |
| 5 | 49323 |
| 6 | 964173 |
| 7 | 21680571 |
| 8 | 551173053 |
| 9 | 15633866379 |
| 10 | 489583062381 |
| 11 | 16780438408539 |
| 12 | 624935780160285 |
| 13 | 25131869565110571 |
| 14 | 1085528359404039117 |
| 15 | 50124679063548821499 |
| 16 | 2464153823558024331645 |
| 17 | 128500643820213560377803 |
| 18 | 7085182933810282490250285 |