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 | 7 |
| 3 | 52 |
| 4 | 407 |
| 5 | 3329 |
| 6 | 28232 |
| 7 | 246552 |
| 8 | 2204895 |
| 9 | 20103027 |
| 10 | 186223399 |
| 11 | 1748009560 |
| 12 | 16591329652 |
| 13 | 158975004204 |
| 14 | 1535725632552 |
| 15 | 14940742412112 |
| 16 | 146259921123407 |
| 17 | 1439658075118967 |
| 18 | 14240062489572485 |
| 19 | 141469058343614452 |
| 20 | 1410975387252602527 |
| 21 | 14122900638031585153 |