a(n) = T(3n,n), where T is the array defined in A025177.

A025185

a(n) = T(3n,n), where T is the array defined in A025177.

Terms

    a(0) =1a(1) =2a(2) =16a(3) =120a(4) =946a(5) =7644a(6) =62832a(7) =522804a(8) =4390056a(9) =37126830a(10) =315770676a(11) =2698179488a(12) =23144461368a(13) =199177780102

External references