Second derivative of n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =0a(6) =0a(7) =0a(8) =2a(9) =3a(10) =0a(11) =1a(12) =1a(13) =0a(14) =0a(15) =0a(16) =4a(17) =5a(18) =6a(19) =7a(20) =1a(21) =0a(22) =3a(23) =2a(24) =2a(25) =3a(26) =0a(27) =1a(28) =1a(29) =0