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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.

A387278 a(n) = Sum_{k=0..n} 3^(n-k) * binomial(n+1,k+1) * binomial(2*k+2,k+2).

Table of values

n a(n)
0 1
1 10
2 78
3 560
4 3885
5 26550
6 180285
7 1221400
8 8272251
9 56062550
10 380361212
11 2583867720
12 17575724491
13 119705522370
14 816297170310
15 5572945684800
16 38088275031435
17 260576833989150
18 1784382167211378
19 12229792774162800
20 83888652677196591
21 575858959975595010

List of values

[1, 10, 78, 560, 3885, 26550, 180285, 1221400, 8272251, 56062550, 380361212, 2583867720, 17575724491, 119705522370, 816297170310, 5572945684800, 38088275031435, 260576833989150, 1784382167211378, 12229792774162800, 83888652677196591, 575858959975595010]

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

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