A184010 n + floor(sqrt(-1+4n/3)); complement of A001859 (except for initial zero).

1, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 103, 104, 105, 106, 107, 108, 109, 110, 111

Offset: 1

Author

Clark Kimberling, Jan 08 2011

Keywords

• nonn
• easy

Crossrefs

Cf. A001859.

Programs

Mathematica

  a=4/3; b=-1; Table[n+Floor[(a*n+b)^(1/2)],{n,100}]

Formula

a(n) = n + floor(sqrt(-1+4n/3))