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A007580 as a simple table

n a(n)
1 1
2 2
3 4
4 10
5 26
6 76
7 232
8 764
9 2619
10 9486
11 35596
12 139392
13 562848
14 2352064
15 10092160
16 44546320
17 201158620
18 930213752
19 4387327088
20 21115314916
21 103386386516
22 515097746072
23 2605341147472
24 13378787264584
25 69622529312665
26 367161088308490
27 1959294979429380

[1,2,4,10,26,76,232,764,2619,9486,35596,139392,
 562848,2352064,10092160,44546320,201158620,
 930213752,4387327088,21115314916,103386386516,
 515097746072,2605341147472,13378787264584,
 69622529312665,367161088308490,1959294979429380]

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Last modified December 22 22:37 EST 2014. Contains 252372 sequences.