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A228980 as a simple table

na(n)
14
216
364
4252
5992
63900
715328
860228
9236624
10929580
113651712
1214344836
1356349296
14221349132
15869490976
163415475172
1713416415184
1852701313836
19207017071552
20813187592388
213194296661552
2212547572276300
2349288333901920

[4,16,64,252,992,3900,15328,60228,236624,929580,
 3651712,14344836,56349296,221349132,869490976,
 3415475172,13416415184,52701313836,207017071552,
 813187592388,3194296661552,12547572276300,
 49288333901920]