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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”).

A220409 as a simple table

na(n)
11
278
3720
410989
5128448
61701214
720736643
8263993960

[1,78,720,10989,128448,1701214,20736643,263993960]