a(n) = ((b(n)-1)+sqrt(3*b(n)^2-4*b(n)+1))/2, where b(n) is A011922(n).

A011916

a(n) = ((b(n)-1)+sqrt(3*b(n)^2-4*b(n)+1))/2, where b(n) is A011922(n).

Terms

    a(0) =0a(1) =3a(2) =44a(3) =615a(4) =8568a(5) =119339a(6) =1662180a(7) =23151183a(8) =322454384a(9) =4491210195a(10) =62554488348a(11) =871271626679

External references