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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.

A047781 a(n) = Sum_{k=0..n-1} binomial(n-1,k)*binomial(n+k,k). Also a(n) = T(n,n), array T as in A049600.

Table of values

n a(n)
0 0
1 1
2 4
3 19
4 96
5 501
6 2668
7 14407
8 78592
9 432073
10 2390004
11 13286043
12 74160672
13 415382397
14 2333445468
15 13141557519
16 74174404608
17 419472490257
18 2376287945572
19 13482186743203
20 76598310928096
21 435730007006341
22 2481447593848524
23 14146164790774359

List of values

[0, 1, 4, 19, 96, 501, 2668, 14407, 78592, 432073, 2390004, 13286043, 74160672, 415382397, 2333445468, 13141557519, 74174404608, 419472490257, 2376287945572, 13482186743203, 76598310928096, 435730007006341, 2481447593848524, 14146164790774359]

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

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