a(n) = T(3n,n), where T is the array in A026323.

A026333

a(n) = T(3n,n), where T is the array in A026323.

Terms

    a(0) =1a(1) =3a(2) =21a(3) =156a(4) =1221a(5) =9828a(6) =80579a(7) =669273a(8) =5612505a(9) =47416278a(10) =402953376a(11) =3440825160a(12) =29498259546a(13) =253737784446

External references