If x is in the sequence then so are x^2 and x(x+1)/2.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =9a(7) =10a(8) =16a(9) =21a(10) =36a(11) =45a(12) =55a(13) =81a(14) =100a(15) =136a(16) =231a(17) =256a(18) =441a(19) =666a(20) =1035a(21) =1296a(22) =1540a(23) =2025a(24) =3025a(25) =3321a(26) =5050a(27) =6561a(28) =9316a(29) =10000