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.

A230071 Sum over all permutations without double ascents on n elements and each permutation contributes 2 raised to the power of the number of double descents.

Table of values

n a(n)
0 0
1 0
2 2
3 6
4 26
5 130
6 782
7 5474
8 43794
9 394146
10 3941462
11 43356082
12 520272986
13 6763548818
14 94689683454
15 1420345251810
16 22725524028962
17 386333908492354
18 6954010352862374
19 132126196704385106
20 2642523934087702122
21 55493002615841744562
22 1220846057548518380366

List of values

[0, 0, 2, 6, 26, 130, 782, 5474, 43794, 394146, 3941462, 43356082, 520272986, 6763548818, 94689683454, 1420345251810, 22725524028962, 386333908492354, 6954010352862374, 132126196704385106, 2642523934087702122, 55493002615841744562, 1220846057548518380366]

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

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