n-th single or isolated number*n-th non-single or nonisolated number.

Terms

a(0) =0a(1) =4a(2) =18a(3) =60a(4) =126a(5) =184a(6) =270a(7) =370a(8) =462a(9) =611a(10) =742a(11) =900a(12) =1072a(13) =1224a(14) =1501a(15) =1660a(16) =1869a(17) =2134a(18) =2448a(19) =2700a(20) =2938a(21) =3429a(22) =3668a(23) =4002a(24) =4650a(25) =5024a(26) =5379a(27) =5678a(28) =6055a(29) =6480