For n weights, number of combinations when limited to two weights per pan.

Terms

a(0) =0a(1) =1a(2) =4a(3) =12a(4) =31a(5) =70a(6) =141a(7) =259a(8) =442a(9) =711a(10) =1090a(11) =1606a(12) =2289a(13) =3172a(14) =4291a(15) =5685a(16) =7396a(17) =9469a(18) =11952a(19) =14896a(20) =18355a(21) =22386a(22) =27049a(23) =32407a(24) =38526a(25) =45475a(26) =53326a(27) =62154a(28) =72037a(29) =83056