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 | 2 |
| 2 | 5 |
| 3 | 19 |
| 4 | 120 |
| 5 | 1084 |
| 6 | 11783 |
| 7 | 141110 |
| 8 | 1791156 |
| 9 | 23646352 |
| 10 | 321220257 |
| 11 | 4459886776 |
| 12 | 63000867229 |
| 13 | 902528825332 |
| 14 | 13080523942476 |
| 15 | 191445447535373 |
| 16 | 2825542818304080 |
| 17 | 42005234042942228 |
| 18 | 628422035415996065 |
| 19 | 9454076958795999908 |
| 20 | 142933849346150225253 |
| 21 | 2170556938059142024688 |