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 | 4 |
| 2 | 21 |
| 3 | 120 |
| 4 | 697 |
| 5 | 4060 |
| 6 | 23661 |
| 7 | 137904 |
| 8 | 803761 |
| 9 | 4684660 |
| 10 | 27304197 |
| 11 | 159140520 |
| 12 | 927538921 |
| 13 | 5406093004 |
| 14 | 31509019101 |
| 15 | 183648021600 |
| 16 | 1070379110497 |
| 17 | 6238626641380 |
| 18 | 36361380737781 |
| 19 | 211929657785304 |
| 20 | 1235216565974041 |
| 21 | 7199369738058940 |
| 22 | 41961001862379597 |
| 23 | 244566641436218640 |