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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.

A378551 a(n) = Sum_{k=0..n} 4^k * binomial(n/2+k-1,k) * binomial(n-1,n-k).

Table of values

n a(n)
0 1
1 2
2 20
3 206
4 2200
5 24062
6 267500
7 3009050
8 34150000
9 390265190
10 4484762500
11 51771831146
12 599921125000
13 6974108163778
14 81297715937500
15 949957147566086
16 11123368187500000
17 130487420114543110
18 1533247106445312500
19 18042303960492212810
20 212590835968046875000

List of values

[1, 2, 20, 206, 2200, 24062, 267500, 3009050, 34150000, 390265190, 4484762500, 51771831146, 599921125000, 6974108163778, 81297715937500, 949957147566086, 11123368187500000, 130487420114543110, 1533247106445312500, 18042303960492212810, 212590835968046875000]

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

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