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Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A146854 as a simple table

na(n)
11
21
31
41
55
621
755
8223
91323
107243
1156001
12498505
135857355
1489335203
151598206021
1635814813801

[1,1,1,1,5,21,55,223,1323,7243,56001,498505,
 5857355,89335203,1598206021,35814813801]