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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”).

A127106 as a simple table

na(n)
11
25
31555
49673655
5187159211791705
6776119592182705

[1,5,1555,9673655,187159211791705,776119592182705]