A183572 a(n) = n + floor(sqrt(2*n-1)).

2, 3, 5, 6, 8, 9, 10, 11, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 85, 86, 87, 88, 89, 90, 91, 92

Offset: 1

Author

Clark Kimberling, Jan 05 2011

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..10000
• Steve Butler and Jia Mao, Problem 11265, Amer. Math. Monthly 114, (2007), p77.

Crossrefs

Cf. A074148 (complement), A103128.

Programs

Magma

[n+Floor(Sqrt(2*n-1)): n in [1..80]]; // Vincenzo Librandi, Feb 18 2017

Mathematica

Table[n + Floor[Sqrt[2 n - 1]], {n, 100}] (* Vincenzo Librandi, Feb 18 2017 *)

PARI

a(n) = n + sqrtint(2*n-1); \\ Michel Marcus, Feb 18 2017