A187318 a(n) = floor(9*n/5).

0, 1, 3, 5, 7, 9, 10, 12, 14, 16, 18, 19, 21, 23, 25, 27, 28, 30, 32, 34, 36, 37, 39, 41, 43, 45, 46, 48, 50, 52, 54, 55, 57, 59, 61, 63, 64, 66, 68, 70, 72, 73, 75, 77, 79, 81, 82, 84, 86, 88, 90, 91, 93, 95, 97, 99, 100, 102, 104, 106, 108, 109, 111, 113, 115, 117, 118, 120, 122, 124, 126, 127, 129, 131, 133, 135, 136, 138, 140, 142, 144, 145, 147, 149

Offset: 0

Author

Clark Kimberling, Mar 08 2011

Keywords

• nonn
• easy

Comments

Apart from first term 0, these are the numbers such that the iterated sum-of-digits (A010888) is odd. - Michel Marcus, Jun 07 2015

Equivalently, numbers congruent to {0, 1, 3, 5, 7} mod 9. - Bruno Berselli, Jun 15 2016

Links

• Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1).

Programs

Magma

[Floor(9*n/5) : n in [0..100]]; // Wesley Ivan Hurt, Jan 02 2017

Maple

A187318:=n->floor(9*n/5): seq(A187318(n), n=0..100); # Wesley Ivan Hurt, Jan 02 2017

Mathematica

Table[Floor[9 n/5], {n,0,120}]
LinearRecurrence[{1,0,0,0,1,-1},{0,1,3,5,7,9},90] (* Harvey P. Dale, May 28 2025 *)

Formula

a(n) = n + floor(4*n/5).

a(n) = 2*n - 1 - floor((n - 1)/5). - Wesley Ivan Hurt, Jan 02 2017

From Chai Wah Wu, Oct 17 2022: (Start)

a(n) = a(n-1) + a(n-5) - a(n-6) for n > 5.

G.f.: x*(2*x^4 + 2*x^3 + 2*x^2 + 2*x + 1)/(x^6 - x^5 - x + 1). (End)