M(M-1)/3, where M is Mersenne prime A000668(n).

A139225

M(M-1)/3, where M is Mersenne prime A000668(n).

Terms

    a(0) =2a(1) =14a(2) =310a(3) =5334a(4) =22361430a(5) =5726491990a(6) =91625444694

External references