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.

A318973 Triangle read by rows: T(n,k) is the number of permutations of [2n-1] that have exactly one preimage under West's stack-sorting map and that also have first entry k.

Table of values

n a(n)
1 1
2 0
3 1
4 0
5 0
6 1
7 3
8 1
9 0
10 0
11 5
12 13
13 20
14 13
15 5
16 0
17 0
18 56
19 136
20 221
21 266
22 221
23 136
24 56
25 0
26 0
27 1092

List of values

[1, 0, 1, 0, 0, 1, 3, 1, 0, 0, 5, 13, 20, 13, 5, 0, 0, 56, 136, 221, 266, 221, 136, 56, 0, 0, 1092]