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A291288 as a simple table

na(n)
01
15
220
370
4210
5546
61260
72640
85115
99295
1016016
1126390
1241860
1364260
1495880
15139536
16198645
17277305
18380380
19513590
20683606
21898150
221166100
231497600
241904175
252398851
262996280
273712870
284566920
295578760
306770896
318168160
329797865
3311689965

[1,5,20,70,210,546,1260,2640,5115,9295,16016,
 26390,41860,64260,95880,139536,198645,277305,
 380380,513590,683606,898150,1166100,1497600,
 1904175,2398851,2996280,3712870,4566920,5578760,
 6770896,8168160,9797865,11689965]