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 | 15 |
| 3 | 93 |
| 4 | 639 |
| 5 | 4578 |
| 6 | 33423 |
| 7 | 246816 |
| 8 | 1838367 |
| 9 | 13788399 |
| 10 | 104011140 |
| 11 | 788315124 |
| 12 | 5998380543 |
| 13 | 45794787678 |
| 14 | 350619595614 |
| 15 | 2691082393818 |
| 16 | 20699166876831 |
| 17 | 159515321712480 |
| 18 | 1231354153215123 |
| 19 | 9519556856284218 |
| 20 | 73694926944160164 |
| 21 | 571201080979318470 |