**a(0)=0. For n >= 1, a(n) = sum{k=0 to n} binomial(n,k) * GCD(n,k).**

*0, 2, 6, 12, 28, 40, 144, 140, 536, 864, 2560, 2068, 12720, 8216, 45192, 78660*

*2 seqfan posts*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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