a(n) = (n-1)(n-4)(n-9)...(n-k^2) where k^2 < n <= (k+1)^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =10a(6) =18a(7) =28a(8) =40a(9) =54a(10) =140a(11) =264a(12) =432a(13) =650a(14) =924a(15) =1260a(16) =1664a(17) =4284a(18) =8100a(19) =13376a(20) =20400a(21) =29484a(22) =40964a(23) =55200a(24) =72576a(25) =93500a(26) =236808a(27) =443232a(28) =728000a(29) =1108380