k appears 2k-1 times. Also, square root of n, rounded up.

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =3a(5) =3a(6) =3a(7) =3a(8) =3a(9) =4a(10) =4a(11) =4a(12) =4a(13) =4a(14) =4a(15) =4a(16) =5a(17) =5a(18) =5a(19) =5a(20) =5a(21) =5a(22) =5a(23) =5a(24) =5a(25) =6a(26) =6a(27) =6a(28) =6a(29) =6