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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 12 |
| 6 | 40 |
| 7 | 164 |
| 8 | 752 |
| 9 | 4020 |
| 10 | 23576 |
| 11 | 155632 |
| 12 | 1112032 |
| 13 | 8733628 |
| 14 | 73547332 |
| 15 | 670789524 |
| 16 | 6502948232 |
| 17 | 67540932632 |
| 18 | 740949762580 |
| 19 | 8634364751264 |
| 20 | 105722215202120 |
| 21 | 1366258578159064 |
| 22 | 18468456090865364 |
| 23 | 262118487952306820 |