A037669 - OEIS

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A037669 as a simple table

n	a(n)
1	3
2	20
3	120
4	723
5	4340
6	26040
7	156243
8	937460
9	5624760
10	33748563
11	202491380
12	1214948280
13	7289689683
14	43738138100
15	262428828600
16	1574572971603
17	9447437829620
18	56684626977720
19	340107761866323
20	2040646571197940

[3,20,120,723,4340,26040,156243,937460,5624760, 33748563,202491380,1214948280,7289689683, 43738138100,262428828600,1574572971603, 9447437829620,56684626977720,340107761866323, 2040646571197940]