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A172261 as a simple table

na(n)
10
20
325
41847
5162531
62501726
721243084
8119138166
9502726650
101724809105
115059647669
1213132889249
1330905051345
1467124176002
15136380034610
16261909043488
17479315827404
18841394145399
191424246670499
202334919892115

[0,0,25,1847,162531,2501726,21243084,119138166,
 502726650,1724809105,5059647669,13132889249,
 30905051345,67124176002,136380034610,261909043488,
 479315827404,841394145399,1424246670499,
 2334919892115]