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 | 23 |
| 3 | 122 |
| 4 | 621 |
| 5 | 3120 |
| 6 | 15619 |
| 7 | 78118 |
| 8 | 390617 |
| 9 | 1953116 |
| 10 | 9765615 |
| 11 | 48828114 |
| 12 | 244140613 |
| 13 | 1220703112 |
| 14 | 6103515611 |
| 15 | 30517578110 |
| 16 | 152587890609 |
| 17 | 762939453108 |
| 18 | 3814697265607 |
| 19 | 19073486328106 |
| 20 | 95367431640605 |
| 21 | 476837158203104 |
| 22 | 2384185791015603 |
| 23 | 11920928955078102 |
| 24 | 59604644775390601 |