Number of solutions to 1^2*k_1 + 2^2*k_2 + ... + n^2*k_n = 1, where k_i are from {-1,0,1}, i=1..n.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =1a(5) =3a(6) =8a(7) =17a(8) =35a(9) =79a(10) =177a(11) =409a(12) =995a(13) =2475a(14) =6336a(15) =16078a(16) =41401a(17) =107304a(18) =279550a(19) =736032a(20) =1950000a(21) =5199850a(22) =13950852a(23) =37576658a(24) =101670863a(25) =276228026a(26) =753114256a(27) =2060995699a(28) =5658663542a(29) =15583477334