cp's OEIS Frontend

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.

A281912 Number of sequences of balls colored with at most n colors such that exactly one ball is of a color seen earlier in the sequence.

Table of values

n a(n)
1 1
2 8
3 57
4 424
5 3425
6 30336
7 294553
8 3123632
9 36003969
10 448816600
11 6022033721
12 86587079448
13 1328753602657
14 21683227579664
15 375013198304025
16 6853321766162656
17 131976208783240193
18 2671430511854158632
19 56709161712552286009
20 1259836187316759240200

List of values

[1, 8, 57, 424, 3425, 30336, 294553, 3123632, 36003969, 448816600, 6022033721, 86587079448, 1328753602657, 21683227579664, 375013198304025, 6853321766162656, 131976208783240193, 2671430511854158632, 56709161712552286009, 1259836187316759240200]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement.