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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 16 |
| 6 | 52 |
| 7 | 170 |
| 8 | 579 |
| 9 | 1996 |
| 10 | 7021 |
| 11 | 24892 |
| 12 | 89214 |
| 13 | 321994 |
| 14 | 1170282 |
| 15 | 4277352 |
| 16 | 15715249 |
| 17 | 57999700 |
| 18 | 214939846 |
| 19 | 799478680 |
| 20 | 2983699498 |
| 21 | 11169391168 |
| 22 | 41929537871 |
| 23 | 157807451672 |
| 24 | 595340479694 |
| 25 | 2250901216266 |
| 26 | 8527700012092 |
| 27 | 32369067177176 |