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 | 4 |
| 3 | 23 |
| 4 | 117 |
| 5 | 454 |
| 6 | 2003 |
| 7 | 9157 |
| 8 | 40899 |
| 9 | 179399 |
| 10 | 796558 |
| 11 | 3546996 |
| 12 | 15747348 |
| 13 | 69834517 |
| 14 | 310058192 |
| 15 | 1376868145 |
| 16 | 6112247118 |
| 17 | 27132236455 |
| 18 | 120453362938 |
| 19 | 534754586459 |
| 20 | 2373975139658 |
| 21 | 10538953415410 |
| 22 | 46786795734201 |
| 23 | 207705902269424 |
| 24 | 922089495910044 |
| 25 | 4093525019450760 |