Partial sums of A009940.

Terms

a(0) =1a(1) =1a(2) =0a(3) =-4a(4) =-19a(5) =-75a(6) =-260a(7) =-464a(8) =5745a(9) =118145a(10) =1638416a(11) =20803836a(12) =258490285a(13) =3203144581a(14) =39595146396a(15) =481418955200