a(n) = A135574(3*n) + A135574(3*n+1) + A135574(3*n+2).

A137223

a(n) = A135574(3*n) + A135574(3*n+1) + A135574(3*n+2).

Terms

    a(0) =3a(1) =18a(2) =234a(3) =1110a(4) =15018a(5) =70998a(6) =961194a(7) =4543830a(8) =61516458a(9) =290805078a(10) =3937053354a(11) =18611524950a(12) =251971414698

External references