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A138457 as a simple table

na(n)
16
281
31875
414406
5219615
6599781
73006756
85864445
918469506
1074264505
11110822520
12320481531
13593409810
14789743031
151346791956
162769558831
175271052035
186438316065
1911304778881
2016009359030
2118913228506
2230381063180

[6,81,1875,14406,219615,599781,3006756,5864445,
 18469506,74264505,110822520,320481531,593409810,
 789743031,1346791956,2769558831,5271052035,
 6438316065,11304778881,16009359030,18913228506,
 30381063180]